ryan.h Posted January 21, 2007 Report Share Posted January 21, 2007 '95 3100, has a random misfire at idle. I have not noticed it at any rpm above idle. You can really feel the misfires hit, and the RPM on the tach drops slightly everytime it misfires (50rpm?). It also seems to have some hesitation or loss of power when taking off from a stop.. Previous owner replaced lots of things, probably trying to get rid of the same misfire. Coils are new. Plug wires are probably new. Plugs are new. You can hear the misfire clearly out the exhaust. No codes set except the for the 3 EGR solenoids, and a cam sensor. I'm cleaning the EGR and passages right now. I was hoping it was sticking open or something, but no luck. Unplugging the cam sensor makes no change in the random misfire. Oh, also there's some red RTV on the UIM, which I haven't figured out how it got there or why it's there... I sprayed everything with carb cleaner and couldn't find a vacuum leak. Quote Link to comment Share on other sites More sharing options...
ryan.h Posted January 26, 2007 Author Report Share Posted January 26, 2007 Well, this weekend I'm taking the UIM off. Here's some pics of the RTV damage: Driver's side: Pass side: Pretty sweet, huh? Also, found some other damage under the throttle body bracket. On top of the throttle body /neck area, there is a rubber grommet thing which leads to the PCV valve and something else on the other side of the engine. Apparently mine was broken off - likely causing a vacuum leak, although I'm not sure it's enough to cause my miss, and it certainly doesn't explain the RTV. (so even if replacing it does fix it, the plenum's still coming off.) Quote Link to comment Share on other sites More sharing options...
Andrew Posted January 26, 2007 Report Share Posted January 26, 2007 why do you refer to it as RTV damage? if used correctly RTV can be your friend. anyway, just looks like someone did a shoddy job with the RTV, probably tryin to fix the same issue. ok here's a longshot. You said you are getting a cam sensor dtc. I wonder if it skipped a tooth somehow, and now you car is running rough because it out of time. Quote Link to comment Share on other sites More sharing options...
ryan.h Posted January 27, 2007 Author Report Share Posted January 27, 2007 why do you refer to it as RTV damage? if used correctly RTV can be your friend. anyway, just looks like someone did a shoddy job with the RTV, probably tryin to fix the same issue. ok here's a longshot. You said you are getting a cam sensor dtc. I wonder if it skipped a tooth somehow, and now you car is running rough because it out of time. Yeah, slathered on isn't "used correctly" Anyways, I pulled the UIM and found out why it was on there... there was a piece of gasket sitting on the lower intake manifold, so I think for some reason the UIM was pulled before, and that piece got stuck, new gasket was installed on top, voila - leak city. So rather than pull it off again, RTV to the rescue! Unfortunately - it looks like it was later repaired correctly, so that's not the cause of the misfire. Good idea on the cam sensor. I unplugged it before and it didn't change anything. One of the UIM bolts was loose (like, finger tight), so maybe reinstalling everything correctly will fix everything. *sigh* Oh - question - what is the 2 or 3 pin plug on the ICM with the purple and yellow wires to? Cam sensor? crank sensor? other? Quote Link to comment Share on other sites More sharing options...
Canada Posted January 28, 2007 Report Share Posted January 28, 2007 The cam sensor and its 6" long pigtail doesn't like all the oil and coolant that leak onto it from the intake gaskets leaking......the wire's insulation gets puffy and pulls back, exposing the wire......which will set the cam sensor code. Check it....its right under the power steering pump....it'll be the worst right at the sensor. You'll need a new cam sensor. The EGR codes......cleaning might not do anything for it....esspessically being digital.....you'll pry have to replace the EGR valve. Both those will make an engine run like shit.... Watch for vacuum leaks....listen for sucking noises. Was the lower intake gasket just replaced? I've seen some guys over tighten the rocker arms and pull them out of the heads......they can be fixed on car though. Quote Link to comment Share on other sites More sharing options...
ryan.h Posted January 29, 2007 Author Report Share Posted January 29, 2007 Fudge... put it back together, fixed some vacuum leaks (broken vacuum lines), cleaned the EGR and it runs 2x worse. It stumbles bad from a stop now. Quote Link to comment Share on other sites More sharing options...
ryan.h Posted January 29, 2007 Author Report Share Posted January 29, 2007 Tested fuel pressure - 39psi @ idle Tested new EGR for vacuum leaks to the outside world - none Changed TPS and reset computer... Ran pretty well for a while, then started putt-putting and rhythmically missing, then back to random misses. Unplugged 3x sensor from ICM - verified that the 3x "low res" crank sensor is only used for spark. Might need to replace that as my next step and/or doublecheck wiring. I need to rescan for codes. Oh - also it is idling at 1100 in park. Quote Link to comment Share on other sites More sharing options...
ryan.h Posted January 30, 2007 Author Report Share Posted January 30, 2007 Wiring to the 3x crank sensor was frayed, but I don't think it's the problem because no matter what I did to it, I couldn't get it to short out. Question - if I disconnect the 24x crank sensor (at the front), will it default to batch fire and still run? Trying to eliminate possibilities..... Quote Link to comment Share on other sites More sharing options...
ryan.h Posted January 31, 2007 Author Report Share Posted January 31, 2007 update - did a cylinder balance test (again) and discovered teh front center cylinder isn't doing much of anything. Swapping plug wires did nothing. Going to swap plugs next to see if the problem follows.... Otherwise I'm thinking injector and/or wiring. Quote Link to comment Share on other sites More sharing options...
ryan.h Posted January 31, 2007 Author Report Share Posted January 31, 2007 scratch that. cylinder compression okay! thank god! Quote Link to comment Share on other sites More sharing options...
ryan.h Posted February 2, 2007 Author Report Share Posted February 2, 2007 Replaced injector and that cylinder's okay now. Back to the random misfire... Also noticed it reved to 2500-3000 after starting warm before settling down. Gotta be a vacuum leak somewhere. Quote Link to comment Share on other sites More sharing options...
ryan.h Posted February 6, 2007 Author Report Share Posted February 6, 2007 Good news: Found another vacuum leak. Replaced vacuum line and it runs without hesitating now. Bad news: Random misfire at idle (only at idle) still there. Even though I checked the output of the crank sensor.... I just cant help but feel it's somehow involved. It just feels like the engine cuts out for a split second. For one revolution or whatever. Also when it was 40 degrees here last week, it ran perfectly without a hitch. Don't know what that was about...... Quote Link to comment Share on other sites More sharing options...
ryan.h Posted February 15, 2007 Author Report Share Posted February 15, 2007 Took it to the dealer. Pissed away $90. Their diagnosis: "just drive it" F_CK. Quote Link to comment Share on other sites More sharing options...
ns87 Posted February 15, 2007 Report Share Posted February 15, 2007 I have the older 3.1, but when my car did the exact same thing I wound up having to replace all 6 injectors. We only did the 2 bad ones, then the other 4 "went bad" within 2 days. Just replace all 6, that might help Quote Link to comment Share on other sites More sharing options...
Canada Posted February 15, 2007 Report Share Posted February 15, 2007 5 injectors aren't cheap. I'd pry just drive it.... Quote Link to comment Share on other sites More sharing options...
ryan.h Posted February 16, 2007 Author Report Share Posted February 16, 2007 I have the older 3.1, but when my car did the exact same thing I wound up having to replace all 6 injectors. We only did the 2 bad ones, then the other 4 "went bad" within 2 days. Just replace all 6, that might help yeah since one injector went bad already, I'd definately be suspicious of the others.... one sticking closed intermittantly would definately cause this. It's retarded to think the dealer couldn't figure out an intermittant misfire though. I think their problem is they're used to getting paid 6 hours and finishing the job in 1. But when it comes to actually doing the work you pay for..... no siree! Get paid for 36 hours in 6 hours because you finished six "6 hour" jobs in 1. Brilliant. Kick out the jobs that actually make you work. Slightly O/T, but I was listening to one of the "salesmen" con this lady out of her money. He was like, "well, in addition to your brake rotors, you need a cooling system flush and we need to change your transmission fluid. We also found this and that and the other which you need to replace immediately. There are a few more things that you can choose to do now or take care of them later... The total is $1972.67." The lady goes, "That's like a car!" hahaha! Quote Link to comment Share on other sites More sharing options...
Canada Posted February 16, 2007 Report Share Posted February 16, 2007 Thats part of flat rate.......there are also jobs that pay 1 hour and take 6! BTW....I can't think of a single labor operation that pays that well (or that shitty). Quote Link to comment Share on other sites More sharing options...
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