gr8shot Posted August 14, 2012 Report Share Posted August 14, 2012 I've had a slight problem for a while now, but recently it's gotten real bad almost un driveable. Here's whats going on... for a while now I've been having a problem with the car having what I'd describe as a slight misfire/cut out whenever I'd give it some throttle in OD with the converter locked, like to pass a car on the highway. Right before it downshifts it'll misfire and cut out. If I let of the throttle real quick so the converter unlocks and then give it some gas to pass a car, it wouldn't cutout or misfire at all, and I'd pass the car no problem. Could easily replicate it, and it hadn't been getting any worse for a while. Until now. Lately it has started doing the same thing but it'll do it when I'm just cruising down the highway, not passing anyone, and it'll do it when I accelerate from a stop now too. And it's gotten worse and more violent. But it doesn't seem to do it until the motor is warmed up. I drive the thing 110 miles round trip to and from work every day so I know exactly how to replicate the problem and what not. It's not a consistent miss like one cylinder or anything. It can be one big cutout that feels like you slam the brakes for a split second, or a rapid succession of small misfires, or a random studder of small misfires, or one small or big misfire or any combination of them, it's completley inconsistent. And most times if I let off the throttle then get back in it, the problem will either go away completley, or almost completely. Fuel mileage is as good as it's ever been, averaging around 29mpg. No codes, no CEL or anything. From all my searching and reading I'm thinking either ICM or fuel pump. The fact it only does it when it's warmed up makes me think it's the ICM, but when the converter is unlocked and it does it, it feels like it's not getting enough fuel, like it's not completely losing power. But I don't know if thats just the unlocked converter masking the feel. Do you guys have any insight? How can I go about testing the fuel pressure? And if the car is still running, will the pump put out lower than normal pressure all the time? I'm not sure what to expect if I do test the fuel pressure, and how to interpret the results. I'm kind of short on funds so I don't want to just throw parts at the problem, but I do need it running reliably for next weekend as we're planning on taking it on a trip to Denver which is about 900 miles round trip. Sorry for the long post, I just wanted to give all the information that I could Thanks! Quote Link to comment Share on other sites More sharing options...
AL Posted August 15, 2012 Report Share Posted August 15, 2012 You can rent a fuel pressure gauge and post the results, also, take a multimeter and ohm check your fuel injectors, autozone can do an icm check too... All of the above is free and can help point you in the right direction Quote Link to comment Share on other sites More sharing options...
Galaxie500XL Posted August 15, 2012 Report Share Posted August 15, 2012 Could be the ICM, but I'm betting you have a dying coil. Keep in mind, the DIS system sends a spark to TWO cylinders, so when one goes south, two cylinders are dropping out...V6's don't run too well on 4 cylinders. I've experienced this twice with my LQ1...I finally broke down and replaced all the coils with newer J/Y parts from a 3400, including the ICM. Quote Link to comment Share on other sites More sharing options...
55trucker Posted August 15, 2012 Report Share Posted August 15, 2012 (edited) A 3.1 engine? I assume were talking OBD I, you say the problem only occurs when the engine has warmed up, try disconnecting the O2 sensor and run the engine in *open loop* under the same conditions, if the problem magically disappears then your O2 is one it's way out. They do *get lazy* when old & tired and can cause this situation of a *miss/stumble*, and the problem is accentuated by the converter when locked up passing the vibration thru the car. One gets on the throttle hard & the systems goes back to open loop and the stumble disappears, (the same when your on the throttle overrun). Edited August 15, 2012 by 55trucker Quote Link to comment Share on other sites More sharing options...
gr8shot Posted August 15, 2012 Author Report Share Posted August 15, 2012 I guess I forgot to say the year, its a 96 so I think that would make it obd2? I don't know what year they switched to obd2. Will the 02 sensor trick still work if it is obd2? Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted August 15, 2012 Report Share Posted August 15, 2012 always check plugs first. the cheapest part. could be a broken plug! Quote Link to comment Share on other sites More sharing options...
gr8shot Posted August 16, 2012 Author Report Share Posted August 16, 2012 I can't imagine it being a spark plug, as if it was it would do it constantly. I actually drove it today, since the alternator died in my chummins. And it was absolutely perfect the whole 60 mile drive. It was cool today 61*f but it didn't misfire a single time today. And I tried several times to make it do it and it wouldn't. So I'm really leaning to the icm at this point. Well see what happens I guess. Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
ricklovin93 Posted August 17, 2012 Report Share Posted August 17, 2012 I can't imagine it being a spark plug, as if it was it would do it constantly.Sent from my Droid using Tapatalk 2 not true i had a spark plug only misfire under hard acceleration, happened to have a small crack on the ceramic insulator Quote Link to comment Share on other sites More sharing options...
gr8shot Posted August 17, 2012 Author Report Share Posted August 17, 2012 Ok was yours affected by temperature? My car runs fine when its cold. And it seems to run a lot better when the outside temp is cooler. Yesterday it was 50* on my drive to work and it didn't misfire at all. Today it was 46*f and it ran perfect again. But Wednesday it was 93*f in the afternoon when I went home and I was worried I wasn't going to make it home! Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
gr8shot Posted August 20, 2012 Author Report Share Posted August 20, 2012 Well I ordered an ICM from rockauto.com should be here in a couple days. The more I read about it the more my symptoms matched a failing icm. I'm not 100% positive that is the problem so my fingers are crossed that it fixes it. We're headed to Denver on Friday so I need the ol gal running smooth. Ill report back if that fixes it or not. Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
rawdeal91vert Posted August 20, 2012 Report Share Posted August 20, 2012 I had to replace all the injectors in my 91' 3.1 convertible. Sounds like a similar problem that I had. It would stall under harder acceleration. The car got progressively worse over a couple of weeks util it would not stay running. The injectors should have nominal impedance of 13 OHMs. Mine were at 2, 4 or 10 Ohms. The car had 73,000 mile on it but sat up for 2 years and was driven very little. Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted August 20, 2012 Report Share Posted August 20, 2012 good luck! Quote Link to comment Share on other sites More sharing options...
gr8shot Posted September 5, 2012 Author Report Share Posted September 5, 2012 Ugh... well it took me a while, but I replaced the icm and fuel filter both to no avail. It is still doing the exact same thing. Cutting out when I load the motor to anything more than normal acceleration. I'm not sure where to look next. Coils? Fuel pump? I can't find a parts store that rents a fuel pressure gauge either Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
gr8shot Posted September 6, 2012 Author Report Share Posted September 6, 2012 Bump for ideas.... ??? Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
virtuetovice Posted September 6, 2012 Report Share Posted September 6, 2012 Have you tried replacing the fuel filter?? Quote Link to comment Share on other sites More sharing options...
gr8shot Posted September 6, 2012 Author Report Share Posted September 6, 2012 Lol I said that I did that in a post above. So ya, no change. Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
willsboattail Posted September 7, 2012 Report Share Posted September 7, 2012 I'm having a similar issues with my 93 3.4L V6 Cutlass !!!!! 1500-1600 RPM moderate uphill grade a stumble in OD until step on the gas. It's like I am lugging the engine at too low RPM in an old car!!??!! Then it shifts down and all is fine! Sound familiar ???? Wondering if it may be a lockup, or other sensor of some type. Putting the car away for the winter, so I'll be researaching this issue all winter. Any Help?????????? Quote Link to comment Share on other sites More sharing options...
Pabz Posted September 7, 2012 Report Share Posted September 7, 2012 Check coils and spark plugs. Either fuel issue or no spark in one/two cylinders. Do you notice nasty smelling exhaust fumes when this occurs? Quote Link to comment Share on other sites More sharing options...
gr8shot Posted September 8, 2012 Author Report Share Posted September 8, 2012 I never smell anything inside the car. If I have the windows down all I ever get is just the normal warm engine smell you get when you open the hood when its warm. And that's only once in a while when I'm in town. Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
gr8shot Posted September 10, 2012 Author Report Share Posted September 10, 2012 Bump for ideas... How do I ohm test the coils? Just across the two terminals on the top? Or do I need to take them off and go from the bottom part that connects to the icm to the top terminal? Not sure how to test them. Sent from my Droid using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
AL Posted September 10, 2012 Report Share Posted September 10, 2012 Top is fine Quote Link to comment Share on other sites More sharing options...
BabyBoyInk Posted September 18, 2012 Report Share Posted September 18, 2012 I think you may have a bad injector. I had the same problem with my 1990 Grand Prix LE. I didn't buy mine new cause they're like $60 each, but went to the local Pull-A-Part and got like 18 of em. After replacing them, had no more problems. Also had a problem similar to that which lasted for about a year. Finally tracked it down to the fuel vapor canister. The original had started leaking charcoal into the vacuum line running from the purge/vent solenoid located near the throttle body. while replacing the vapor canister, I found charcoal throughout the entire vacuum line. Replacing one (or both) of these should fix your problem. I'm sure of it. Quote Link to comment Share on other sites More sharing options...
Crazy K Posted September 20, 2012 Report Share Posted September 20, 2012 autozone has a rental fuel gauge... Quote Link to comment Share on other sites More sharing options...
Scott205 Posted September 22, 2012 Report Share Posted September 22, 2012 it would help if you knew if it were losing spark when this happens. It could be a Crankshaft Position Sensor (CXP) or the wiring maybe shorting when the torque hits, help to know if it were sparking or stopped sparking.. I have found the ICMs usually work or fail, I bought mine at Autozone (lifetime warranty) becuase they were failing every year and it is so much trouble on a 3.1 or 3.4 DOHC to dig them out. Quote Link to comment Share on other sites More sharing options...
gr8shot Posted September 26, 2012 Author Report Share Posted September 26, 2012 (edited) I tried replacing the icm a couple weeks ago to no avail. I did get a CEL and a couple codes. I have a couole intermittent EGR codes so I didn't bother to read the codes for a while. But when I did I also had a p0303 and a p0102. Cylinder 3 misfire and maf out of range or something maf related. I cleaned the maf not too long ago with the maf sensor cleaner but have gotten that code again once since then. Today on my way to work cruising down the interstate at 70 like always it was running great then out of the blue there was a huge misfire that shook the whole car violently for a split second then was gone. Ran great til I got almost to work and hit a train at a crossing. It started sputtering and reving up and down a little and died while I was sitting there idling in gear. Started right back up and ran fine the rest of the few miles to work. I'm going to stop by vatozone and see if ours has a fuel pressure tester for rent and see if that's the problem. I've read soooooo many threads about folks with this problem. Many have replaced the entire ignition system... plugs, wires, coils, icm, then fuel injectors and still not fixed the problem. I'm kinda frustrated. But on a good note I did an oil analysis and my motor with 228k got a perfectly clean bill of health after running 5500 miles on Dino 5w-30. Sent from my Droid using Tapatalk 2 Edited September 26, 2012 by gr8shot Quote Link to comment Share on other sites More sharing options...
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