Kevin Lee 487

Car was running really goofy lately on and off. Sometimes it would run great, others made me fearful to even be in traffic.

The Symptoms
Sometimes when I started the car, it would run rough and have an SES light. Turning it off for 10-20 seconds made it run normal again.

When driving the car would sputter and lose power ( as if I was completely letting off the pedal ) and the tach jump up and down to match. This happened on the highway once and I pulled over, put the car into park and waited maybe 15 seconds and it was fine the whole way home after that. It even died out on me once after sputtering especially bad.

I figured the Plugs and Wires were bad ( since the plugs I had on there were half Vatozone cheapass and half MSD streetfires ) and the plugs hadn't been changed since I got the car a year ago.

Bought some good AC Delco plugs and MSD Super Conductor wires. Symptoms did not improve.

So some actual research this time leads me to check the codes and look up my symptoms. ECM threw a code 36 at me which in conjunction with my symptoms, pointed to the MAF sensor. Tried to outright replace it first and when Autozone gave me 2 bad ones ( only 2 they had ), I said screw it and got some MAF cleaner just for the hell of it.

Symptoms completely went away. Throttle was more responsive and the car drove perfectly ( well as perfectly as it can for a 24 year old car with near 200k miles )

Fast forward a week and one day, the car throws the SES light at me at startup and runs rough. I shut her down, thinking the MAF cleaner only provided a temporary fix. Check the codes....code 12. Wtf? I thought that OBDI stored the codes for you to check them later. Car started fine after I checked the codes and drove fine.

It threw the SES at me once more today and I noticed throttle response was down and lo and behold. Theres the stutter again. ( Happens above 30mph )

So again, I clean the MAF and the symptoms go away. I check the codes again.....still just a code 12. Just out of curiosity I checked the TPS. .49 at idle and 4.5 at WOT. Seems a little off, but the symptoms and cleaning of the MAF timing raises too much of a red flag to think the TPS could be causing this.

Since I got the car a year ago ( ~ 2500 miles ), I have replaced the following
Entire distributor setup ( cap, rotor, Ign coil, ICM, PUC, Dist )
Plugs and Wires
In-line fuse
Courtesy fuse
12 gauge wire off the starter for the main fusable link ( symptoms were present before and after this was replaced )
And of course an oil-change and brakes / rotors

Sounds like its time for a completely new MAF?

hdis2002

iTrader: (1)

Fix one thing at a time. The TPS voltage should be .54. You aren't way off but still. Fix that first. It does sound like your MAF is being a little problematic, however, a vacuum leak at the plenum can also cause it to run rough and give you a MAF code. Did you disconnect the battery before you replaced the MAF sensor? I had to do that when I replaced mine. Not sure what the problem was but it wouldn't run right until the ecm was reset. Since then it has run fine. My MAF is from Advance Auto so it's probably the same thing as Autozone. Good luck and let us know what happens.

Steve

Kevin Lee 487

Yea I cleared the codes when I re-connected the MAF. It just seems too much to be a coincidence that the car suddenly runs great the minute I clean the MAF.

I will however, adjust the TPS and check for a vac leak for the umpteenth time. Been scouring for one in hopes that it was what is causing my AC Vents and Defrost not to function at all.

hdis2002

iTrader: (1)

Well, that's interesting. based on your last post, it sounds like you've got a vacuum leak if your climate controls aren't working either. Been there, done that one too. I replaced all of my vacuum tubing to fix the problem. There were hairline cracks in the old stuff that I couldn't really see until I removed them. Get a vacuum gauge. That's the easiest way to figure out if that's the problem. Your vacuum should register 14-15 or better at idle. When you shut the car off, it should hold for a bit and go down very slowly. You're bringing back some memories of my 87 IROC project.

Steve

PDX88IROC

Hello, I am not a total expert, but would like to share my opinion and similar experience.

In my opinion, my short answer would be "yes". Although, you said you tried two from AZ and they were both bad. How do you know they were bad? I'm assuming just because they didn't fix the problem? If so, something else seems to be the "common denominator".

So my experience was with my '88 IROC 305 TPI 187,000 miles. It would also run great for about an hour, then the SES would come on, and it would start to cut in and out and have me looking for the nearest exit on the freeway. My codes were 33 & 34 (Hi and Low MAF reading) and from what I read here decided to change both the MAF relays and also picked up some MAF cleaner. This fixed the problem for a little while (very little since I hardly drove the car), but it did it again and code 34 came back, so I replaced the MAF with a remanufactured one and all has been good since. And I have been driving it much more often and for longer durations since. I must have gotten lucky with the reman one, and maybe you were just unlucky with two bad new ones. It sucks that they cost about $300, but at least they only take a few minutes to change. Although mine has that original "clamp" on the front connecting to the air filter intake that is a real pain to get back on. The vacuum leak is a good suggestion too. Have you ever tried changing the relays. They are pretty easy to get and cheap too.

PDX88IROC

That is so true Steve. I recently had to replace my thermostat, and removed the thottle body to do so. The technician who usually works on my car (who I wasn't going to pay $160 to change my therm) did give me some good advice to watch out for the one on the bottom of the TB that I guess is known to become very brittle. Here is a pic from my thread on that project (now I know why it isn't a 15 min job).

https://www.thirdgen.org/forums/atta...3-img_3934.jpg

Kevin Lee 487

Looks like I might have my work cut out for me then. Thanks for the suggestions.

Kevin Lee 487

Well this is strange.....After adjusting the TPS, ( .53 at idle and 4.2 at WOT ) the car pulled its shtick of " Hey Im going idle like crap and throw an SES light with no codes! " ( Keep in mind this entirely random. Cold, hot, raining, sunny. It has a mind of its own.

Turned it off and restarted it immediately and it ran fine.

The strangest thing though is that the vents are sort of working for the first time since I got the car a year ago. The defrost vent is blowing strong and I can definitely feel a feel faint blowing out of the main vents with the exception of this vent here. Though they are not blowing cold air. That would have been a miracle. Though that was about a year ago that I put freeon in the AC system. Never to actually use it.

hydrolic144

iTrader: (2)

Fellow digital dash! Love those things.

My GTA too had a ugly idle and was all weird and had never thrown a code a me, never. So I was around the passenger side plenum and just so "happen" to unplug the vacuum line from the EGR solenoid that goes to the bottom of the throttle body and the charcoal canister and it awoke! I mean literally. Idle was smooth as ice and car has been right ever since. No codes or drive-ability issues either. But def check out vacuum lines for sure.



But skipping that. Sometimes the Relay is the culprit as well. One of the 3 that are mounted on the driver side firewall right next to the brake booster. Can't miss it.

Kevin Lee 487

I'll definitely give that a check Hyrdo. Aside from the ICM going out on me after a 2 1/2 hr drive in 90+ degree heat, I NEVER once had ANY problems with it running oddly or doing goofy things when driving. It was always very smooth and I drove the car 25 minutes city one way to work 6 days a week for 3 months plus errands and what not.

That sort of thing started happening when I had the Dist. replaced in the winter. They also adjusted my timing without consulting me. Idles right on 500 now and I'm always scared when driving because it sounds like its going to die but its just how the car sounds lol.

So just for clarification, you unplugged it and the car ran better? Or the other way around?

norcalz28

iTrader: (13)

When is the last time you adjusted you IAC for min air? I had a bad TPS that would not let the car go into closed loop. Ran very strange and took me a little while to figure out why. Installed a new one, dialed it in, bingo. Do you have access to a smoke machine, that's the best way to check for unmetered air leaks. if your car is going into closed loop and you can notice a difference once it's warmed up, I'd look at other components. I know my iroc would run much better with the stock motor when I set min air and adjusted the tps.

Will

Kevin Lee 487

Ive never touched the IAC and no I do not have access to a smoke machine. There is also no difference when the car is cold or hot. If it decides its going to start goofy, it does it.

First start of the day, engine fully warmed up after driving around, start in the middle of the night after its cooled off, etc. Its entirely random. Like I said in my first post, immediately after I cleaned the MAF BOTH times,( letting it air dry before re-installing ) the car ran fine and I noticed an improved throttle response.