I apologize if this is a duplicate post. I have searched this forum and the Internet for weeks trying to get an answer. I have a 1995 lumina 3.1. It seems to idle fine, but when I am driving it sort of hesitates when I start from a stop and when the car shifts gears. I decided it was time for a plug/wire change, which I did. For about two weeks it ran great with no hesitation but for the last couple of days it has been back and bad as ever if not worse. I don't know what else to try. I tried braiding the plug wires because someone somewhere said would help. I did notice that the old plugs all had a lot of greyish buildup on them when I removed them. That's probably a sign of a different problem. Also, I replaced the plugs with the kind of plug that had two prongs on it. I don't know if that was a good idea or not seeing how they have a very small metal piece in the middle and could probably get fouled up easily.

I edited this post to add that I also noticed that one of the posts on the coil pack(?) on the far left has a rusty connection. Could his be something I need to replace also? I cleaned it well and took most of the rustiness off, but I didn't do that unilateral it started acting up again. So it was working fine even with the rust right after the plug and wire change.

Anyway, I'm rambling now. Any help would be greatly appreciated and if anyone needs more info just let me know and I'll
do my best to provide it. I'm not a mechanic though so I don't know how technical i can get.

thanks in advance.

Welcome to AF, hesitation means many things to many people, is this a misfire/engine roughness or a " flat" spot? From here we cannot determine what is acually happening.

This is a misfire I beleive. It's not something that happens every time. It's almost like it gets no gas for a second and then catches up. Usually if i push the gas it takes a second for the car to get power back.

Like to help but this is too vague for any meaningful advice, if the plugs and wires are new and properly secured, check fuel pressure.

take a 3/8 extention and drop it on your fuel injecters one at a time but dont hit the to hard .this will knock out the dirt in the end of the injector

I had the fuel pressure checked and they said it was normal. I had a replacement fuel filter installed just in case. I also had my injectors cleaned. The car is still acting up. I want to scan the computer to see if it is throwing any codes, but I don't have a scanner. I understand that you can use a jumper wire to check codes on an obdi dlc connector, but my obdi connector doesn't have a b wire to jump the a wire to. Is the connector screwed up or am I not going to be a able to check it this easily. I tried checker auto parts, but they only scan obdii.

Would you think that a seafoam treatment in the pcv valve might help? I'm guessing it's misfire now that I took care of the fuel system. They guy who did it said my throttle body was filthy, but I can't see what else it could be now.

i also just pulled all the plugs to see if they were fouled up since new plugs helped so much before. All of the plugs looks fine. They have a little crud on them, but it doesn't look like they are so fouled up that they aren't sparking.

I did want to ask also if a rusty connector on an ignition coil is a problem. I haven't been able to find much info on this, but i noticed when I changed my plugs and wires that one connector on the 5 2 coil pack is rusty. I guess I should check for spark, but I don't know if it would make a difference at idle since it only seems to have problems when the engine speed drops as I slow down or when the car shifts gears.

I suppose it could also be some sort of air flow problem. I replaced my air filter when I did the plugs and wires. Would it be best to check the 02 sensor, the MAF sensor, or the MAP sensor first?

well I decided to replace the coil since the part wasn't a horrible price, but that didn't help the problem.

I was also wondering if this could be an EGR valve problem. I noticed that the EGR valve is located just past the throttle body assembly and the guy who cleaned out my injectors and fuel system said the throttle body was bad. Could crap have gotten into the EGR valve during the cleaning or, if the throttle body was fouled up, could that be a sign that the EGR valve is clogged? How would I test to see if the EGR valve is working properly. I found a ton of videos on youtube, but they were all on a different type of valve.

it could be the module under under your coil pack or your maf sensor but really sounds like one of the coil's in coil pack.

Like I said I replaced the coil with the rusty terminal. But it didn't help.

Did the guy clean your throttle body? He said it was dirty but did he clean it? It really hard to tell what kind of hesitation you are having like Maxwedge said. It sort of sounds like you might have an ignition misfiirng situation when you are under high vacuum conditions like between shift, but I'm not sure. I think you should use original AC type plugs gapped around .045. Check the coil primary (and secondary if you happen to have the coils off) and ignition wires resistance. Look for vacuum leaks. It'd really help if you could get a scanner on it, but you have that wonderful '95 OBD 1.5 that no one seems to have the scanner for. Just for sh1ts and giggles see what happens if you unplug the EGR connecter wire.

He cleaned the throttle body. Do you mean I should drive
it with the egr disconnected? I unplugged it and let the car idle until it was
warm. Then I revved the throttle. I saw no difference
when I did that. I thought about switching back to regular plugs, but why .045? Spec is .060

OK did you drive it with the EGR connector unhooked and no difference? The reason I suggest a .045 gap is I was thinking your spec was .045 and not .060, but also because sometimes .060 is too much and gives problems. If the spec calls for .060, use that or tighten it up to .055 or so. Is this hesitation you are getting kind of jerky feeling (most likely ignition) or is it more like the engine just flattening out (most likely fuel injection related)?

I didn't drive it with the egr unhooked. I only let it idle and used the throttle to rev the engine. Why would regular plugs be better for this car than the others? Just wondering. It's hard to describe the hesitation. Almost always it kind of jerks a couple times and then feels like it has no power until it revs back up. Sometimes when coming to a stop it does the same, but without the jerking. The closest thing I could describe it to is like trying to start a standard from a stop in third gear.

People have had problems using non original plugs. The o.e. plugs will give you o.e. performance. Revving the engine in neutral won't tell you much. You have to drive it under the same circumstances that caused it to act up. What you desribe sounds like it might be an ignition misfire.

Ok. I guess I'll try different plugs. After changing the one coil I thought might be bad I don't know what else to try. Especially since new plugs worked
last time, even though it was short lived.

Ok. I guess I'll try different plugs. After changing the one coil I thought might be bad I don't know what else to try. Especially since new plugs worked
last time, even though it was short lived.


You are better off with the AC plugs even if it doesn't solve your hesistation. Maybe you can return the other plugs. My suggestion is to check the resistance of the wires even if new, and the coil secondaries at least. That's easy to do.

I'll have to pick up a multimeter and do that.

Any idea what proper readings would be?

As a guide coil secondaries should 5-7K ohms. Wires less than 7K.

OK. so I was looking for information on how to test the coil packs. I found a lot of stuff, but none of the information I found seemed relevant to the coil packs on this car. The only exposed metal to test is the terminals that the ignition wires connect to. On the bottom of the pack there are two slits that tabs go into. I'm honestly not sure what I'm even doing now.

Measuring between the the terminals on each coil is the secondaries. The two slots or prongs on the bottom of the coils are the primaries. I wouldn't worry about the primaries for now.

I haven't gotten to test the coils and wires yet. But just for the hell of it I did unplug the egr this morning and drove it a bit. I noticed no difference at all in the way it drove.

did you do as i said?

JD, no. Rather than taking a chance with tapping the injectors I had them cleaned instead. I hope that would be the same or better.

do it i m tellin you, you wont regret it

How did you check the coil that you changed? Did you use a spark tester or timing light to check for spark before replacing that coil? Did you use the di-electric grease between the coil & the ICM when installing the new one?
Have you had the ICM tested? How many miles on the engine?
Does it jerk really bad when starting out from a stop?

Sorry it's been a few days since I posted, this weekend was hell with homework.

Bearwulf,
I checked the coil with a multimeter. But that was not until after I replaced it. Before I replaced it noticed a rusty terminal and decided to swap it out anyway. When I tested it with the multimeter it checked out fine, but I had a hell of a time finding a spot on the terminal that would read through all the rust. So I'm still glad I swapped it.

I did use dielectric grease between the coil and the module, but it really probably didn't need it, there is a spacer there and there is a rubber gasket type thing separating the plugs that insert into the bottom of the coil.

I have not had the ICM tested, I guess I probably should, but this is my only vehicle, so taking it out would leave me with no way to take it somewhere to have it tested.

The engine has 156,000+ miles on it.

It does not jerk really bad when starting from a stop. The hesitation usually happens in between shifting gears, but not at all like a slipping transmission. It will complete the gear change, but when the RPMs are low after the shift, it bucks and the RPMs drop, then it has to catch up. The same thing happens when I slow to a stop, without the bucking part.

:runaround:

So, I switched out the spark plugs like I was recommended to do. Crazy part is, immediately after changing the plugs, it ran like a champ again for about 35 miles, then it started doing the same thing again. I tested the wires, all check out at less than 4k ohms. The ignition coils were weird. The coil I replaced read at 8800 ohms, while the other two read at 5900 and 5800 respectively. The old coil that I replaced read at 5900 ohms once I was able to get a read on it through the rust. Maybe faulty new coil? or maybe all three were weak?

Anyway, because I ran into my uncle from PA this weekend, who is a mechanic, he told me I should swap out the PCV valve and check the EGR valve. I swapped the PCV yesterday and noticed that it had a cracked vacuum elbow boot attached to it, which I replaced hoping that might correct a vacuum leak. NO GO. I pulled off the EGR and it was pretty darn clean. A little bit of carbon build up, but all the valves moved freely and there were no clogs in the tube or the valves. I cleaned it all off anyway and replaced it, while changing the gasket. I drove around for a bit and it still has issues.

I decided to check my 02 sensor. My chilton manual tells me that I should use a test light, which I don't have currently, for the first part of the test, so I skipped that. The second part said I should use a multimeter to test the resistance between terminals A and B on the o2 sensor wiring harness. I tried for about 30 minutes, but I could not get any reading. Possible o2 sensor issue? or maybe I'm just doing something wrong.

At this point my only guesses are o2 sensor or MAP sensor, I suppose I could change out the manifold air temperature sensor also, but I tested that and the resistance readings seem to be within spec according to my chilton manual.

Any advice?

Well usually if you had sensor that was off or maybe a lazy 02 sensor it would set a code but not always. What you described with the jerking when the engine slows sounds like it could be the torque converter. Have you checked the transmission fluid level and condition? It probably really needs a fluid and filter change anyway, but it might be too late to clear up a TQ/trans problem if it has one. It's hard to tell what's goping on from here but my guess is it it might the trans.

i really thought that it might be too, but I really can't see how the problem would have been completely eliminated and the transmission would still shift fine immediately after changing the plugs twice now. I also just had the trans fluid checked, and was told it was fine, haven't looked myself though. I have no idea when the last filter/fluid change was though.

There is obviously a code being set, which is why I was trying to figure out if I could jumper this stupid OBD1.5. The light will come on, but it always resets after the car has been off. Once I turn the car on, the light is off and stays off for a few minutes, but then comes on. The light does not seem to affect the hesitation though, because it runs the same whether the light is on or off.

i really thought that it might be too, but I really can't see how the problem would have been completely eliminated and the transmission would still shift fine immediately after changing the plugs twice now. I also just had the trans fluid checked, and was told it was fine, haven't looked myself though. I have no idea when the last filter/fluid change was though.

It is probably coincidental that every time you work on the ignition it runs good for awhile. The thing about a torque converter acting up is it will run good untill engine warms up and lockup is activated then when you hit that speed around 35-45 mph it will show up. Does it jerk around this speed?

There is obviously a code being set, which is why I was trying to figure out if I could jumper this stupid OBD1.5. The light will come on, but it always resets after the car has been off. Once I turn the car on, the light is off and stays off for a few minutes, but then comes on. The light does not seem to affect the hesitation though, because it runs the same whether the light is on or off.

Yeah I had forgotten that you have that obd 1.5 that you can't pull codes on. I didn't know or had forgotten that you were getting a check engine light. Sounds like you have an intermittent problem and it'd sure be nice to know what that code says. Heck, for all we know it might be a transmission related code lol. Instead of throwing parts at it, you might be ahead to find some place that can at least read the codes if not diagnosis the whole problem, or maybe you could buy a scanner that has the adapter and can read these '95 OBD 1.5 setups, then return the scanner.

if you werent getting the correct reading on your o2 sensor, your engine may be running SUPER rich... i would make long test leads to test your o2 sensor while you sit in the drivers seat and warm the car up ( just idleing ) and make sure the value dosent change as the car warms up - thats how the o2 sesnor works -off of exhaust heat---- that sensor tells the engine computer what the air/ fuel mixture is as far as what is comming out of the exhaust, if its to hot, it's to lean, the engine adds fuel to cool it down, if its to cold it leans it out by reducing the amount of fuel in the current mixture (within certain perameters). it sounds like you have a bad o2 sensor telling the computer to add to much fuel! i'd change that next, i bet thats your problem! its kinda like driving with the "choke" on. i think thats why you keep running thru the plugs too!

also before you install the new o2 sensor, test the new one the same way you tested the sensor in your car if the new sensor passes the same test your original o2 sensor failed , theirs your problem!! if it has the same results.... you can try it but it most likley wont fix the problem... good luck!

Besides at what speed, I forgot to ask does it run rough cold right away or does it have to warm up and go into closed loop? That could point to the O2 sensor or the TQ either one. Not sure why you weren't getting a reading from your O2 sensor, but like I said it'd be nice to read the code that is setting.

i don't know if I would say that it jerks at 35-45 mph, but it definitely runs more rough, kinda like I hit a really bumpy road, between 35-60 mph then levels out.

it always runs rough right from the start.

*just a side note* - i just drove to the gym and back and just for the hell of it I shifted into neutral everytime I had to come to a stop. If I shift to neutral when stopping, the problem with slowing down doesn't happen. Looks like it may be transmission related after all.

Although, my uncle did tell me that I could get a result like that if the car was running rich, he said it would be like the engine floods itself as it is trying to slow down and then smooths out once it begins to idle. So I guess, if he's right, it could still be o2 sensor.

I suppose it wouldn't hurt to buy a new one and test it the same way I did my old one. I'm just leery after all this about putting in another unneccesary part.

I suppose, apart from buying a scanner that could read this OBD1.5, I could buy one of these diagnostic cables I have been seeing online that I could plug into my mac, I might be able to get even more information from that than from a scanner.

Do they work?