MAF TPI 350

No codes.
ECM reset by 8+ hour battery disconnect.
CAI installed, but was acting like this before the CAI was installed, so not likely a cause.

For the first 1-2 minutes (hot or cold engine) after starting the car, the idle is ROUGH. Like between 350-450rpm. When cold, it won't hold that idle & dies. When hot, it will hold that idle, barely. But in all instances, it runs fine after +-2 minutes And then drives (doesn't try to die at a Stop sign, etc.) fine.

What confuses me is that it does it hot or cold. I can even go drive 15min down the road, come home (up to 180/190 operating temp) & it idles great at about 650rpm. Kill the engine, start it right back up 10 seconds & it acts just like it did when I first started the car. Rough idle for a minute (smooths out faster when engine is hot).

It kinda reminds me of the ECM going into a Learning mode every single time I start the car & won't "remember".

Any ideas?

 

And the complete distributor (not HEI), cap, rotor, coil, etc. are all only about a year old. No new plugs or plug wires.

 

TPS? If I use a flat bladed screwdriver to slip in to the throttle stop to bump the idle up, it idles nice & smooth.

New TPS is only $34, but I don't spend $ on testing parts without further indication that the part is defective.

 

I read something about adjusting the TPS (haven't tested it yet) but nothing about HOW to adjust it.

My engine seems fine above idle, which suggest an isle sensing (throttle position) issue. Am I on the right track? How is the TPS adjusted if the voltage between open & closed reads wrong?

 

I did eventually get a code 33 (High Air Flow Indicated) but it clears after resetting the ECM & doesn't come back, usually, yet still idles like crap.

And now once it is warmed up, it idles ok & clears up much faster.

 

My 86 305 TPI has the same issue. What was wrong with yours? Some of the posts are missing or I can't see them.

 

No posts are missing, just that nobody but you has responded yet.

I'm still fighting my issue. I discover that the plug on the IAT valve is shot to hell, so I'm replacing it first & hoping a bad connection is the culprit.

I know my error code says MAF, but I am hoping to find another issue, since the MAF is $150 & my car runs fine after warming up.

Just odd that the low idle points towards the IAT. The stumble just off idle points towards the TPS. And the dieing while cold but runs "good" after warmed up, points towards the O2 sensor. I could just start throwing parts & money & see what fixes it, but I don't work like that.

 

Yea, I don't want to start throwing money and parts into it either now knowing what is wrong. If you ever figure it out message me and I will do the same. I'm about to park mine for the winter so I may not find out till next spring.

 

I suspected my IAT, since the primary problem is at idle, so I unplugged it just to see if there was a bad connection or who knows. My plug literally came apart. The 4 wires in it are arranged 2x2. 1 stayed plugged in & its wire pulled through the plug & the other 3 unplugged & went different directions. Needless to say it could simply be a very bad connection, so I ordered a new plug to wire in. I'll get it on Sat.

 

Given the fact that I have open exhaust currently, I dare not take mine on the road, but I too have a horrid idle/dying situation. just over idle it sounds great and healthy and when I give it some good throttle it is down right vicious.

The sensor you are referring to that has 4 wires in a "2x2" arrangement is called your IACV.. idle air control valve. fyi

Please make sure to let us know on your progress as things go along so others in the future can see a thread that has an actual solution.

 

Yeah...I knew, just wasn't thinking straight when I typed it out. My bad.

What is odd to me is that when the engine is cold, it won't start without a touch of gas pedal. Then it idles ROUGH, until it is fully warmed up then runs perfectly fine. Drives fine. come to s stop & idles fine, etc.

Turn the engine off, let it sit for 10 (ish) minutes while in a store, come back out & the idle is ever so off, yet goes to a perfect idle within a minute, when the engine is warm.

Shouldn't a bad MAF/bad IACV wiring/bad whatever cause bad running, regardless of engine temp? If it wasn't for the bad col/good hot, I'd think TPS since the biggest part of my issues are just off idle. Hot/Cold points towards the IAT. And CFL code says MAF, but how can the MAF be good at hot but bad at cold, and bad when hot first the first couples minutes of start?

I should have the IACV wiring tomorrow & get it put in Sunday. Doubt that will solve my issue, but will eliminate 1 possible problem while fixing something that needs fixing.

 

I keep hoping the bad IACV wiring connector is just giving a false reading to the ECM, since it only seems to happen at idle & just off idle.

 

What is are the 2 electrical plug "thing" (sensor?) on the front of the block above the timing cover, just below the IACV?

One directly below the IACV & the other right beside it, in the middle of the engine? The middle one seems to be broken & have no plastic section for the plug to hook to, just 2 electrical stubs sticking out to plug on to. Plug has 2 wires,1 black, 1 yellow. Coolant Temperature Sensor?

No idea of the other sensor beside it wire colors, as I have not pulled away the loom to see, but anybody know what that sensor is too?

I got the new IACV plug today & plan to splice it in tomorrow (if not tonight) to replace my broken one.

 

Here is a pic of the broken sensor. Not sure what it is or what the other 2 sensors are. Anybody know?

Since I'm having running issues & find a broken sensor? You never know what could be contributing, since not every single sensor sets an error code when broken. What sensor is that, so that I can replace it? What is the sensor to it's left too?

 

OK, even though I'm not getting any real help, other than the guys having issues too, I'll keep talking about it & even if I have to solve it myself? Others with the same issues might find this later & it will help them.

IATV connector replaced, no change. I didn't really expect one, but the connector was FUBAR'd so it needed to be replaced as a possible cause.

Now I'm getting 36 (MAF burn-off relay) not 33 (MAF), but the really odd part is that once it goes into Closed Loop the idle REALLY smooths out. PROM problem? Idles at best 450 in Open Loop, but perfectly smooth at 650 in Closed Loop. This is making me hesitant to buy a MAF. Almost pointing more towards a bad PROM, despite the 36 MAF code. If the MAF is bad, then why does it idle smoother in Closed Loop?

 

no tpi expert but that looks like an important temp sensor in your pic. code 36 is a bad burn off relay if i remember? should be on the firewall? if its not working correctly your maf sensor can get built up with crud. theres probably a thread on here about setting your tps. a service maual can walk you through it too. youll need 3 short pieces of wire & a multimeter. id also check for vacuum leaks & bad grounds. clean every connection you can. i went through something similar once only to find the timing was way off. i guess the computer was compensating for the wrong timing? hope you guys find your gremlins.

 

My whole distributor, cap & rotor is brand new, only the coil was reused.

36 is the burn-off relay, but I had gotten 36 erratically for over a year with no bad running issues, so I got to where I started ignoring it. Sometimes it would come on, sometimes not. Real inconsistent.

I was getting 33-MAF until I replaced the IACV connector. No more 33-MAF code now but now 36-MAF Burn OFF Relay instead. I wasn't getting 36-MAF Burn Off Relay while getting 33-MAF.

The Burn Off Relay is on the firewall next to 2 other relays. 1 is identical so I'll try swapping the plugs from one relay to the next.

What confuses me most is how it can run bad in Open Loop & so good in Closed Loop. But even when it gets to running great, I can shut the engine off, restart the car right away & it runs bad again although for a much shorter time before it goes into Closed Loop. That points toward a PROM issue, in my head.

 

ok, maybe I missed it, but what year is your car/engine?

88 and older had a "Cold start injector". 89 and up did not.

If your 88 or older, perhaps the CSI is bad.

 

87.

CSI, you mean cold start injector? Test method for that?

 

yeah. I have an 88 and I have a similar issue, unfortunately, mine goes deeper as even after it warms up, I still have a serious bog...
I think the completely unscientific way to test it to to simply disconnect it and see if the idle changes.

new cold start injectors are hard to come by it seems. 89 and up TPI systems got rid of it and the computer just compensates for the lack of that extra injectors at cold start.

I'm going to just program mine out.

 

When does the CSI function? Ambient temp requirement? Because mine can warm up until it runs perfectly fine, turn off the engine & restart & the problem occurs again, just for a much shorter time period.

 

Just doing research on this myself righ tnow so I dont have al the answers yet.

But It seems the CSI runs when the Cold start switch tells it to. So your switch may be bad as well (Or instead of)

Found this thread that shows and tells more about the Switch
https://www.thirdgen.org/forums/tech...-305-need.html

 

Looks like the same one I asked about above, with a pic, but I only got 1 response on it & I actually found the answer before I read it, but no biggie there. FSM wasn't clear, but the Haynes showed it clearly with a pic. First time I've ever liked the Haynes over the FSM!
https://www.thirdgen.org/forums/post...54-post14.html

Looking Online, nobody local has one, so it has to be ordered. I know mine is broken so it needs to be replaced, just wasn't sure that it was a cold start-only sensor or just a temp a sensor for the ECM. Since it is broken, it could very well be the cause & needs replacing anyways.

 

wow. that sensor isnt cheap either....

 

Where did you find it? My broken one is the one on the right in those pics. http://www.autozone.com/autozone/par...questid=455577

https://www.thirdgen.org/forums/tech...-305-need.html

 

THe one on the right is just a temp sensor. $8-$20 at Rock auto..... THe one on the left is the Cold start swich.

http://www.rockauto.com/catalog/moreinfo.php?pk=86930
$136 at ROck Auto.

lowest price I found was still over $100

 

Replacing any part of the cold start system is a bad move. The need for that system can be removed with a proper chip. I had an '87 and burned an '89 chip to remove the system. Worked great for many years. That whole thing was just a band-aid from GM.

 

Can a bad MAF be my problem? I get a bad MAF code, but it only runs like crap on first start up, hot or cold. Only difference is that if it is already hot, it smooths out much faster. That points towards it NOT be the CTS.

Summary....Runs like crap on start up hot or cold. if hot, smooths out MUCH faster. Regardless, it feels like an occasional miss at cruise RPM. And the only codes I've gotten are 33-MAF & 36 MAF Burn Off Relay. 33 stopped & now just 36. Sometimes no code at all, but runs like crap anyways.

 

Well, not everyone can just burn chips, so what choice do we have besides replacing the part? We have to find a 89 chip or replace the part?

 

My point was more toward the idea that it does not cost $136 to start burning chips.

 

you dont necessarily have to burn your own either.

http://www.pcmforless.com/index.php?...per&Itemid=312

(Never used these guys.. I ordered my own burner and cables, but ifyou are just looking to bypass the cold start system, this may be an option and gain a few hp's in the process.)

 

It was a bad MAF. Replaced it today & all is well now.

 

good idea to replace your relays for it also. If you haven't