How to read a VACUUM GAUGE and DIAGNOSE engine issues

I recently installed a vacuum gauge on my Jeep Cherokee XJ and would not like to explain why. In this video I will explore how to use a vacuum gauge to diagnose engine issues as well as how to use it to determine instant MPG
How to install a vacuum gauge:
• MPG Vacuum Gauge - EAS...
Checkout the D&E Store for awesome Jeep and
D&E MERCHANDISE:
teespring.com/stores/de-in-th...
We hope you enjoyed this video and will keep in mind that all information included is intended to be purely academic and in fact is only the opinion of D&E. We are not professionals, nor are we qualified to knight you a professional. D&E want to ensure that anyone modify or fixing their own vehicle does so in a safe manner which leaves the vehicle in a legal, roadworthy state. In short, DON'T BE A MONKEY WITH A TOOL BOX! If you don't know what you are doing, leave repairs and modification to the professional.

[@mrkultra1655]

Thanks man. It’s sad how many people have either forgotten about or just don’t know about using vacuum gauges. The miracles of modern technology are just leading us down the garden path to oblivion.

[@grntchstrmdws]

Thank you for this. I recently acquired a 94 GMC K1500 Suburban (159,000 miles) with a vacuum gauge installed. I'm still getting it put back in shape so I haven't driven it enough to know the vehicle yet, but that vacuum gauge is no longer a mystery and I consider myself fortunate to have it there on this still "unknown" truck.

[@mikeypotts4732]

Thank you for sharing! Thought I had a restricted exhaust but was able to rule that out with a vacuum gauge and watching your video!

[@bradyf8351]

I know it’s a long time since this was made but I’m really glad I found your video. You really do an amazing job at explaining in a very thorough but not overly complicated way. Thanks you for the information

[@markharris4592]

This a brilliant video, you made it really simple to understand. Thanks for taking the time to put it together !! I'll be out looking at my van this weekend with the vac gauge now I know what to look for.

[@Bambulancer]

Just starting my mechanic’s certification. Thank you for clearly explaining what manifold vacuum is.

[@davidforte964]

You’re exactly right it’s the forgotten gauge, I installed one in my 80 trans am great video.

[@paulanderson388]

Love that 4.0 drone...XJ's forever!

[@skip741x3]

Audio is fine brother...Very info dense video , you know ur stuff! this is a goldmine of advice and tips for both novice and experienced mechanics... thanks man!

[@howski724]

Thanks for all the great info on your channel. I used to have a 74. Fj40 a long time ago. I used to be a bit of a cruiser snob but I really like my XJ. It’s inexpensive to get one in good shape and easy to work on, easily modified and up graded. Plus all the info, videos and advice out there has you covered on whatever may go wrong. I looked at a fj60 wagon (used to have one of those too) outrageously expensive. I’m a convert.

[@DEInTheGarage]

Nice. How does the XJ compare to the FJ?

[@pablochavez9087]

Awesome info. Thanks for the video

[@ProjectDanH]

Seriously? Giving all this sweet vacuum info while your attention is divided on the road! Pretty impressive. I can't even express a simple thought standing still. Haha.

[@DEInTheGarage]

Haha.. I usually rehearse my videos on my commute anyway, so on this day I just turned the camera on to save time!

[@ProjectDanH]

@@DEInTheGarage brilliant!

[@vinnydelucia2510]

And at the end where you say your willing to help out. Now that's top notch. Good man!!

[@Mrgberry2]

This is outstanding. Thank you for this I don't have instant mpg and this is a mod I'm going to do

[@danielshearer5016]

ty good video n great advice, said on the level.

[@highlevelbars]

Damn you did a great job at explaining this. You managed to hold my attention for the entire video 💪 subscribed.

[@bradyf8351]

I like how you explain things. I am a subscribe now glad I found your channel you are really easy to understand and follow along with please keep the solid content coming

[@mikewilson8594]

Excellent video. Period!

[@shsshs3895]

Thank you for the video. Very good explanation of how and where engine vacuum is created. Have not encountered any other youtube video that explained how and where engine vacuum is created.

[@Odenix75]

Thank you my friend, English is my second language and you have a special way to explain things that I understand very well I couldn't get how to wire a relay and a switch until I saw your video. God bless you I appreciate you, keep up with the good work!!

[@ProjectDanH]

Yes.. explained it very well.. While driving the entire time!

[@DEInTheGarage]

Thanks for the feedback! I am glad you are finding the videos helpful. Cheers!

[@MSTrishRN]

That was amazing! You taught me something today. Thankyou

[@DEInTheGarage]

I am glad to hear that! That is what we are here for. haha

[@treyskrobarczyk25]

Awesome video

[@PitbullRescuer2113]

Thanks for your efforts. I’m subscribed and binge watching the information you’ve provided. You rock!

[@DEInTheGarage]

Thanks! Glad you enjoyed the content!

[@PitbullRescuer2113]

D&E In The Garage, it’s the content and the details. You know your shit. I subscribe to quite a few vehicular focus channels but this channel is a lot more valuable knowledge wise than any on my list. Keep up the great work.

[@DEInTheGarage]

@@PitbullRescuer2113 it is very rewarding to have someone say that. We make these videos to spread some knowledge, so it is awesome to hear someone thinks we have accomplished that. Thanks!

[@halseyballistic]

Outstanding explanation!

[@DEInTheGarage]

Thanks! Glad you enjoyed it

[@danhambrick6331]

Thanks for the tip....

[@davidm3210]

Good stuff -keep motorin'

[@thedobermangang3503]

very good video my brother

[@Jarhead6154]

Dude awesome video, thank you for putting this out there, this is a great help for me since my WJ has like 206k miles on it and I'm going to look at doing this here in the next week or so. Another great way for me to tell how well my engine is doing (for the time being), even though I am putting money aside to end up getting a new motor or possible rebuild my engine for my WJ. And no matter how you guys record these vids it's always informative!!

[@DEInTheGarage]

Well thanks for the feedback! I will try to keep the quality up in the future, but glad you didnt mind in this one. Sounds like you have some cool plans for your WJ. I would like to rebuild the engine in my XJ, but time and money are tight...

[@Jarhead6154]

​@@DEInTheGarage I can completely understand the money and time being tight, I am back in school and doing what I can on the side or over time is what I have to do, to put money away and all that. So whenever I have everything in place then I can work on getting it worked on.

[@DEInTheGarage]

@@Jarhead6154 Good for you, man! Gotta do what you gotta do, right?

[@liviudaniel5082]

yep,very good video,lesson!big thumb up!

[@nicholaskelley4191]

Definitely gonna pick one up for my wj in the morning

[@TheBeardedJeeper]

Great video! I learned a lot. Definitely think I need to install a vacuum gauge in my Cherokee

[@DEInTheGarage]

Yea man... It is a really good idea on those old 4.0s.. Keep an eye on them. I am pretty sure my valve train is all sludged up which I would not have looked into before noticing the odd readings on this gauge

[@PitbullRescuer2113]

I grabbed one for $15 at harbor freight (boost/vacuum) to diagnose a slight misfire its a 2” white face gauge with LED backlighting. My issue is mounting it.

[@TheBeardedJeeper]

Raymond Sugel Jr harbor freight is amazing!

[@gustavette8487]

Great video. Very clear and comprehensive. I just subscribed. Question: when you check your idle vacuum level to see if it in the healthy 18 - 21 level (8 cylinder 350 small block) should you check it in PARK or in DRIVE (with the break pedal on of course)? Thanks

[@icemule]

Don't use propane, just ask Hank Hill, lol. Don't eat the Fugu, just ask Homer Simpson. I wish wifes 92 had OBD2, My 97 Maxima has one and I can read vacuum on that with a dongle and free version of the Torque app in real time as your driving, very, very helpful in telling you that their is a problem. I didn't even think about putting one in this Jeep. 90% sure I'm putting one in now since there is not an OBD port on her XJ, THX!

[@DEInTheGarage]

It is really easy and - especially for a non-OBDII vehicle - the information you can gain about engine status is invaluable

[@vinnydelucia2510]

My man, great video and your explanations are too. Now, you may just want to add in how cams will change vacuum pressure as well. Cams with more duration will cause less vacuum and someone may think they have issues with engine, when in turn , they may have a different cam in there second hand purchase car. Thanks, bro

[@jtmoffroad]

Nice king of the hill reference haha. So much good information in this video and i learned a good bit. I’d be curious to see what mine is like. I suspect my rings are going cause it seems like it has some blow by. I would think if it’s specific cylinders leaking then the vac gauge would jump around as well? I’m gonna have to get a vac gauge now and also make a custom metal dash to make all the gauges look purdy!

[@DEInTheGarage]

Haha... who doesn't love having more gauges to look at while driving...

[@stinesautocare5990]

Got me with the gray beard 😂

[@js2music231]

Hi. Think you for sharing your knowledge. I have a question about the vacuum gauge number I’m getting which is 15 steady at ideal,engine at operating temperature. You said in you video that number 15 can a bad ring issue or timing chain. I’m having a p0300 code misfire and with the vacuum reading of 15 where should I start at the timing chain or piston ring or both?

[@coronaxj5599]

Nice info loved, now i know what to do with guage info , in my xj 97 I'm use a cheap Ebay obd2 Bluetooth adapter with torquepro app in my phone, i you can see real time info, delete bad code, o2 sensor up and down graphics, vacum, fuel flow, close loop etc, and use overhead console computer to read real time mpg and regulate my foot, take one of the junkyard Cheers from mx lml

[@DEInTheGarage]

Dang.. That is a pretty good idea. I will have to look into that a bit more. Thanks for the feedback and suggestion!

[@bascondavid]

Good day, Nice information, you passed across. I use a carmy 04 model v6, Pls i got a vacuum reading of 25 at idle which seem to be quite steady at idle and every quite steady still (25) at higher revs above 1500rpm. What's does that mean someone pls tell??

[@BlairMaynard]

That headliner really ties the car together.

[@edgarlopez4995]

AWESOME THANK YOU I WILL PUT IT IM MY TACOMA 22

[@AzzuriCaesar]

hey man, really like the channel. Is there a chance you could do a video on exhaust leaks- how to diagnose and fix them on a cherokee. Thanks, i’m suspicious of one but don’t know how to confirm or find it.

[@DEInTheGarage]

Hey, thanks for the support. I think we can try to put something together for sure. Keep an eye out in the coming weeks

[@howski724]

Love the channel, was wondering if I could ask you about a steering column problem I am having. You seem really knowledgeable, was thinking you could steer me in the right direction ( pun intended). Thanks!

[@DEInTheGarage]

Haha.. yea, that is why we are here. What is your steering issue?

[@datsdylan007]

What’s your vacuum going down the hw, I have a 4.0 ranger on 33s and I’m at 7-8 psi on the hw

[@kendallmakesfoodaywhmf5541]

very informative, also you sound exactly like eddy burback

[@DEInTheGarage]

Huh... I will take that, Thanks!

[@selecttech6532]

I recognize that opiate high on the way to work.

[@chrisvanderslot5212]

Cool story!

[@thedobermangang3503]

what should my vacuum gauge read with a camshaft thats alittle bigger than your stock cam ..i have a 1990 k5 blazer 350 engine it has rebuild with up graded the cam to a howard rattler cam intake lift 225 exhaust 535 duration 227/235 lobe separation 109 centerline 103 i check to see how mush vacuum i were getting and its no where near 19 to 21 of mercury .. the needle is in the red area sitting on 10 where it say late value timing or leak at intake manifold or heat riser

[@abdelrehmanalmohammad4409]

i have a problem i hope u can help me i have a mustang 2015 v6 and i have a vacuum/boost real time reading built in in my car.. in the traffic ( brake ) Rpm drops and rises ( below 1000) feels like the car want to die and the vacuum drops to 0 to 3 and 0 again ( while stopping ) and brakes feels so stiff i have to use emergency brakes .. when i give it a throttle it loads up reading rises in the vacuum/boost guage for 5 seconds only and then goes back to 0 + bad performance delayed throttle while accelerating all the time and when i hardly accelerate a fuel or gas smell comes from the ac vents .. i changed brake booster + vacuum hose almost everything and still i have the issue .. please advise what could be the problem

[@fadingveil]

Can you tell me what my problem might be if my engine bogs and loses vacuum/ power when shifting into 3rd? Idling at 17/18 , when driving it lowers between 10-15, and then shifts to 3rd and it bogs down and vacuum drops to below 5 . No power and starts dieseling

[@wes1934]

So, the amount of vacuum is inversely proportional to the amount of engine load? [ie, high vacuum = less load; high load = less vacuum .. ?]

[@kennethlindahl9206]

19 thru 30 I collected and repaired 70s toyota corollas I figured out how to time with a timing light a vac gauge and screwdriver and they would purr glass of water smooth ( that is where ya put a glass of water on your valve cover and no ripples) I did this to every one I owned and a bunch I didn't own havent tried it on a jeep .....yet

[@DEInTheGarage]

Haha... I'd like to see a vid of someone tuning a carborated Jeep with a vac gauge

[@kennethlindahl9206]

@@DEInTheGarage If I get a 4 banger 84 you will see one

[@donjuan7519]

I have excessive vacuum from my dipstick oil dipstick what causes that

[@brandonshopbell1713]

I have a 1998 Jeep Cherokee with about 17 in.hp. and just installed a permanent vacuum gauge today Ellen looked up your video. You said 15 wasn't the best. So what is the best in.hp for a 1998 Jeep Cherokee

[@DEInTheGarage]

Should be around 18-21 for a very healthy engine

[@ObamaoZedong]

Dumb question but I can't find the answer anywhere. Does the propane method for finding vaccum leaks work for a diesel?

[@DEInTheGarage]

Yep, works for diesel too!

[@jamiewilliams9974]

Ok I have something crazy... I bought a 1978 f-150 with a 460 motor 2 years ago. I didn’t know anything about engines when I first got it so upon learning what a PCV valve was I installed one correctly. previous owner had just a rubber hose just hanging there. So now I have solved that vacuum issue along with many other issues🤣. Now I’m driving down the road and all of the sudden my truck is running quiet which scared the shit out of me because I thought it cut off initially. I put a vacuum gauge on it and what do you know it’s at a solid 20. So I’m excited gotta throw 2 qts of oil in it, was starting to hear the rockers chatter no big deal it’s still running smooth so I go to the auto parts store throw oil in it and... dmnnit back to square one,with the pressure back at 15-12 sporadically and a little smoke coming out the left pipe. It’s loud again. How is that???? It’s good down 2qts of oil but now at level it’s messing up? What the hell ? Can anyone figure that out?

[@jamiewilliams9974]

Oh yeah and I figure because it didn’t have that PCV valve the oil was seeping past the piston rings causing it to smoke but now it only does it to the left side tailpipe and only when I’m in neutral/park

[@howski724]

How does that FJ compare to an XJ? That’s like comparing apples to oranges. My FJ had a stroked 350 Chevy power plant (383 stroker) small block 400 everything. Tons of power but it ran hot. The journals were thinner after it was bored out so you had to keep an eye on the temp in the summer desert wheeling. So in that respect the two are very a like. But I would compare it more to a FJ60. My FJ was a battle tank. Totally underpowered though. Stock straight 6. It was a dog. I even pulled all the smog and air crap off it so it would do 70 max, on the freeway. It was an 1987. The XJ is much more fun to drive. Much faster and lighter. I like the way the XJ feels off road too. Light and quick, plenty of power but there is always that thing in the back of my mind about the axle strength. Never had to worry about that with the FJ60. Might need to upgrade the front axles and ring and pinion to put my mind at ease. The XJ has a beast of a motor. I love it.

[@DEInTheGarage]

Oh dang.. That sound like quite a Toyota you had! I can definitely agree with you assessment of the way the XJ feels off road. I love it. Thankfully it is not too difficult to swap gearing or even axles on the XJ

[@howski724]

Hell again. Steering issues, finally took the steering column out started to take it apart to fix it and a bunch of little broken plastic pieces fell out of the upper housing. Bummer. From what I can tell the spring/clip that keeps pressure on the top of the toothed bar above the toothed gear that the key cylinder turns fell out from wear and tear. So as you turned the key the bar would just ride up and not engage the ignition. Not sure I could get it back together even if I had the right parts or even knew the parts to order OR where to get them. Sooooo I just ordered a used column off eBay. Problem solved, just have to wait a bit. No more starting the Jeep in the wet rainy parking lot shorting the started with a long screw driver. That’s were it broke.

[@DEInTheGarage]

Haha.. Dang.. Sounds like a fun issue. Can;t say I have heard that one before

[@donjuan7519]

Hey I have excessive vacuum from my oil dipstick and the oil

[@donjuan7519]

Fill hole on the valve cover

[@NordicBloodshed]

What if i have a Diesel engine? Will the gauge work if connected to the vacuum pump?

[@DEInTheGarage]

Yes, will work the same

[@NordicBloodshed]

@@DEInTheGarage thanks mate

[@fasterthanaturtle]

Wouldn't mpg be a direct correlation to pressed gas pedal? How is vac mpg different?

[@DEInTheGarage]

Have you ever heard someone explain an internal combustion engine as basically a large air pump? If not, that is a common way people break an engine down to its most basic function and it is accurate. The vacuum being created by is a direct comment on the eficciency or work an engine is doing.

[@fasterthanaturtle]

@@DEInTheGarage Thank you. I understand the importance

[@skip741x3]

@@DEInTheGarage spot on!

[@johndavis5055]

Nicklaus

[@arthurmoore1524]

This guys got a good video, but I'd like to throw some ancient knowledge at you a wise man once taught me. THIS IS THE PORTED PORTION OF THE ARTICLE: - PORTED vacuum is above the throttle plates of whatever you're working on. If it's above the point where fuel and air actually go into the open hole in your intake/plenum, it's ported. This vaccum is created when the the throttle is opened or partially opened, because there is a passage being covered by the throttle plates or "butterflies" in your carb or throttle body. These passages are dormant and covered or "closed" when you're at resting throttle. The more rpm you create, and tbe throttle open, the more vaccum this port will build. At idle you should have NO vaccum, or very very veeeerrrrry little. PORTED vacuum is going to be how much air and fuel are being processed on the vaccum Guage when you're accelerating. A slow climb is inefficient @ wide open throttle. It should be a steady, swift, climb when accelerating. OLD SCHOOL GUYS ( PORTED) This is where you'll want to hook your modulator valve/transmission vaccum because it dosent have any vaccum at idle. Your modulator / transmission vaccum is only going to pull so much, you're better off to be at no vaccum when waiting at red-light/idling because this has less stress on the diaphragm inside the modulator valve, and will be more "snappy" or responsive and will have a better , more fulfilling "climb" when it's hooked into this port. Besides, on gm applications, the Modulator Valve has an adjustment screw, it's been a long while, but I'm pretty sure the screw Orientation is (CLOCKWISE makes a tighter/firmer/quicker shift. COUNTER-CLOCKWISE will make a looser/longer/softer Shift. Don't quote me, research) ××××××××××××××××××××××××××××× THIS IS THE MANIFOLD VACCUM SECTION: Manifold vaccum is crested as soon as the engine fires. Its the suction from inside the engine (glorified combustion air pump) this is you're efficiency side. This is going to be the vaccum created UNDER the throttle plates. INSIDE the "intake (MANIFOLD...) " This is a way monitor efficiency. This is where you'll know if you've got any kind of internal problem. As you give it all the onions at wide open , the needle should drop to almost 0, and slowly climb. When you let off the gas, it should come about 5in or just a little above where it initially started, then level out where it originally was. Issues: - fluctuate at idle - leaky valves or worn/broken valve springs, worn valve seals, leaky Manifold gasket (ex: intake, fuel device) Fluctuations while driving - bad rings, bad valves/bent valves, dirty fuel/fuel delivery. Erratic needle- leaky intake, valve adjustment wrong (you probably broke valves or bent valves at this point), bad lifters, dropped lifters, worn cam lobes, Off balance crank (usually balancer or flywheel) but usually a really bad vacuum leak. If it pops and sputters, probably a vaccum leak. WHEN TUNING MANIFOLD: FOR MPG- you want to be around the enrichment circuit. this is when you're optimizing fuel to air delivery. You want the leanest/most air you can get in, while the least/less amount of fuel, all while still retaining a good idle speed and smooth idle. This will give the best fuel economy, but that's mostly on you. Hook up a Guage in yourcar, you want to drive as if there's an egg between your pedal and the floor. The more vaccum you make at less throttle going down the road, the least fuel you'll burn (given the enrichment circuit is close to your setting, every carb and throttle body is different on location of circuit. Pls research) FOR POWER: you want the to be behind the enrichment circuit, or "rich", but the key element is the curve of your ignition and how "hot" The ignition is. You can dump all the gas you want, if you won't be able to ignite it all in the combustion chambers (a.k.a. spark delivery) then you're just fouling your engine and wasting gas for a weaker result.. OLD SCHOOL GUYS (MANIFOLD) A STEADY reading with a less lumpy cam, you'll have some needle movement if it has a radical cam. This is also where I tend to hook my vaccum advance. You're set at a more "retarded " point of timing by the constant pull of vaccum. This allows you to creep up on your max amount of timing you can squeeze out of it. While retaining big end spark for the most optimal "pull". EXTRA PUNCH FOR THE OLD SCHOOL GUYS: This guy left us out, I got u tho -to tune vaccum advance curve- The easiest way I've found, is hook to the PORTED side first. This will show how quickly you build rpm, and how much. The quickness is how your distributor advances from its lowest degrees of timing. Adjust the distributor to perform as good as it can on this port. THEN HOOK TO MANIFOLD. When you "thwhackkk" on that throttle, as we know, should come almost to 0, then slowly climb, you'll be in the ballpark from the ported tuning you did on your canister, this is where you'll fine tune. You want this needle after its drop to 0 to climb as quickly as possible. I hope this clarifies some stuff for those who still don't understand . Vaccum isn't a very hard concept.to grasp. Use your ears, get a Guage, and use your eyes. Smell, smell for lean mixes and rich mixes. Taste your oil for any gas. Don't be scared. It Won't physically hurt you.

[@arthurmoore1524]

For epa complaint vehicles: Ignition vac: ported Trans vac: ported or Manifold. Wherever its happiest Non compliant: Ignition- manifold Trans- ported

[@wilfredocortez8327]

too much talking

[@smileyfromthestreetz8624]

My car is idling high around 1500 rpms, I bought a vacuum gauge and my car is at 25 inches of Mercury. What would be the cause of this?