I'm having this cold start problem. I thought it was a bad MAF because I was getting a MAF high error code. It was also dying in stop lights when idling. I checked the MAF relays with a tester, cleaned the connectors, fixed some vac leaks, and now the MAF code is gone and doesn't die in stop lights (I feel more power also). I monitored it with WinALDL also, and the MAF readings look great, very consisntent with RPMs. BUT, the cold start problem is still there.

I tried disconnecting the cold start injector, and it wont even start (just cranks forever), so this means that the CSI is working. I also discovered that when I start cold and drive it for about 5-10 blocks so it just slightly warms up, then shut it down and restart (a la Windows LOL), idle smoothes out and the car just runs great until I start it the next morning again. BUT, if the next morning I disconnect the MAF it starts fine and idles smoothly. Any ideas on what could this be??? Please help!

 

The car doesn't use the MAF until after it's running.

Anyway, have you checked your CTS? Your symptom sounds similar to the problems I've experienced when the CTS tanked and told the computer it's -40* outside.

 

You sure about that Jim? I thought the MAF was used at startup?

Anyway, when mine went south, I couldn't start the engine for beans, disconnecting it, and it would fire right up and idle fine.

But before running out and replacing it, I'd test or try replacing the relays first.

 

MAF numbers are useless until the car is running. When you crank the car, not nearly enough air is going past the MAF to mean squat.

 

Thanks for your posts guys!

I just checked the last WinALDL data log and the MAT numbers are threes and fours and just until a good while (about 10 min later), it gets up to twenties. There's definitely something wrong with that sensor, so I'm going to check it and replace it if necesary.

I did some searches on MAT and found out that on a MAF TPI its only used to control the opening of the EGR valve. Is this correct? I also found that I have EGR readings in my logs even when the MAT sensor is still giving readings of threes and fours. Is this right?

The coolant temp sensor is giving good, consistent readings, so it's not that. What else could it be?

 

mine does the exact same thing,and i mean EXACT same thing,do you get an SES light when its cold in the mornings? then it goes off after a 5 block drive and restart?

 

Your cold start injector is nothing more than a fuel injector. It is subject to the same conditions as a fuel injector a.k.a. could be clogged, leaking down in need of rebuild.

I provided rich at cruzin performance my complete set of injectors and the cold start for a rebuild and flow match.

 

Can anybody tell me what happens when I disconnect the MAF? Does it go into limp mode? Does it still use the CSI? Why does the problem go away when starting without the MAF? Maybe I should just wire a switch to my dash to disconnect MAF in cold starts and then connect it again once it has warmed up? LOL

MarkB:
I tried getting codes this weekend, but had to use WinALDL to read them because my dash doesn't work. This time it started right up and idled nice. Maybe because diagnostic mode (the one with a 10kohm resistor) raises idle speed to around 900rpms? Anyway, I started it and had no error codes at all, but no idle problems either. I'm going to try to fix my dash (bad contact or short maybe) and see if the SES light lights up on cold mornings

MikeInAZ:
Would I be better off if I just disconnect the CSI and modify my chip to not use it? Does doing this makes the ECM to adjust cold start crank injector pulse?

Jim85Iroc:
The car fires right up, but idles horribly. I think it is using the MAF at this point.

Thanks for your replies. Please keep them coming.

 

I'm not a big fan of making modifications to correct an existing problem. I like to fix stuff and then modify it if necessary.

One thing.... never trust an SES light because it is a bulb that does burn out. So I would recommend borrowing a buddies Auto X-Ray or such to pull your codes.

Disconnecting the MAF would cause an instant code 33 which would put your car into limp-home mode. This mode enriches the fuel mixture so would act as a "choke" in a round about sense.

I believe that is why it starts easier with the MAF disconnected.

 

Yesterday I had my wife crank it cold. Once it got going on its own, I disconnected the cold start injector. Guess what... no change. I think this means the CSI is not the culprit here.

Has anyone with this problem fixed the bad idle like mine by replacing their maf?

Please help. I'm set on fixing my TPI. Everyone in my country just swaps a carb. I want to be the only one to keep the TPI.

 

Blaze...now you're kinda' losing me.

Once the car is going on it's own it doesn't "need" the cold start injector. If it's having trouble getting started or warmed up I would suspect the CSI is malfunctioning.... BUT there are other possibilities.

The CSI is nothing more than a "choke" for a Tuned Port Engine.

If you are having idle problems there are things to check such as:

1. The EGR port inside your plenum (usually clogged with soot).
2. The fuel pressure.
3. Fuel Filters (tank and inline).
4. TPS voltage.

You must check the codes. Period.

If you have problems they will show up as trouble codes.

If you have MAF problems you will have a code 33 or 34 or 36.

 

Hello Blazer79,

I recently had a problem with my 89 Iroc where the rpm just started going crazy while I was driving the car. It was going up & down, sometimes almost dieing on me. Thought it might be some bad gas so I stopped at a station & filled up with some good gas (93 octane). Barely made it home in limp mode. Checked all my relays and they were good. Disconnected my MAF sensor, engine cranked right up and ran good. Reconnected the MAF sensor, started engine and it ran like sh*t. Disconnected MAF relay and MAF burnoff relay one at a time and started engine, same problem with each. Replaced MAF sensor and haven't had a problem since.
Just my two cents of thought.

PS: no codes were showing until after I disconnected the MAF sensor.

The Trickster!!!!!!!!!!

 

MikeinAZ:

Sorry if I confused you but english is my second language. In cold mornings, the car cranks, and fires right up, but idles horribly. I disconnected the CSI in case it was remaining open even after the engine was running. What really confuses me is that there are no codes at all. MAF readings look normal. They increase accordingly as I raise RPMs with my foot.

Thank you for your suggestions:

1) I haven't checked inside the EGR port. What I did was to disconnect the vacuum line that goes from the EGR solenoid to the EGR on a cold morning with the engine running (like crap of course). Then I sucked and pumped air to the disconnected hose that goes to the EGR, and was able to control the EGR position. If I opened the valve, idle would get worse and eventually die. If I closed it right before it died, idle got back to where I started (crappy, but running). So I don't think it's EGR. Besides, EGR has nothing to do with the MAF which makes my idle good if I disconnect it. All that could do is move the valve to the point where I moved it manually.

2) That's something I can't check right now because I don't have a gauge. But wouldn't that affect idle ALL the time, not just in cold mornings? Also, again, wouldn't that be ruled out by the fact that disconnecting the MAF brings me good idle?

3) This car once did get a clogged filter, and I couldn't get it past 2500rpms. I currently can rev it up all I want, so I'm thinking maybe not again.

4) TPS voltage was the first thing I corrected. I did it with WinALDL, and adjusted it until the computer saw the correct voltage.

As I said before, there are no error codes. However, there are a few readings that deserve attention:

1) MAT readings start with zeroes, then ones, then sevens... then 21s. Then it makes a jump to 79 all of a sudden. That was one day. Another day it started from threes and progressively increased to 28. I think this sensor is definitely defective. But, I read that this sensor only affects the CSI. That's why I tried disconnecting it right after starting it, just in case it remained open.

2) VSS fail error code: I only got this until my last reading. I was getting speed readings every time, except the last day. I don't think this has anything to do with cold start idle though, since it's always stopped.

3) O/D flag: The computer always think it's in overdrive. Could this be the culprit?

Do you have any more suggestions?



Trickster:

I'm starting to think maybe it is the MAF, but I really want to rule out everything else first. For the price of the MAF, I could get a new set of 24# injectors that I need for my 350 swap. Also, what if I replace it and idle is still the same? I can't just return it back to the store. I have to buy stuff in the US using a freight forwarding company in Miami, so nobody would reimburse my shipping and import taxes. That's why I really want to make sure everything else is fine.

Thanks for your replies!! Please give me more suggestions. I'll try everything you tell me.

 

If you have a "good" friend who has a car similar to yours with a good MAF. Beg, plead with him (or her) to borrow it to test in your car to see if it is indeed the MAF sensor that is bad. Maybe they will be nice to you.

The Trickster!!!!!!!!!!!!!

 

Blazer79,

Sorry I didn't mention this in my last post, mainly because I just thought about it a few minutes ago. Here is something that you can try on your MAF sensor, remove from your car and take a can of electrical contact cleaner and spray it into the sensor to clean any oily residue and dirt off the sensors elements that has accumulated there over the years. I'm not saying that this will cure your problem, but I have had it cure one I had with a MAF sensor several years ago. Good luck!!!!!

The Trickster!!!!!!!!!