flightform89

Hi everyone. Thanks for reading this. -Yesterday,I had a few muffled backfires when coming to a stop.Engine seemed to run mostly okay,but I sensed a reluctance in it's performance(best way I know to descibe it).Now it shuts off immediately after starting.If I work the throttle,I can keep it running(barely),but it stumbles badly with a few more muffled backfies.When the motor shuts off,I can hear the fuel pump. The car had 93000 miles when I got it 6 months ago,and I've put about 11000 miles on it since.The engine is stock,and this is the first problem I've had with it. All my previous cars have been carbed,and after much searching and reading,I'm still really stuck here.-Thank you for any advice you can offer,Dee.

flightform89

Follow-up to above.Could this be ignition based?-as in a bad rotor and/or distributor cap. I have a '77 firebird(broken rear-end) with a good cap/rotor that I could use.

vwdave

Mine did that. While its giving you the problem, stop the car, and unplug the timing connector (like you are going to time the car) and see if it'll run. If so, do the diagnostics of a code 42.

flightform89

Do you mean that if the car runs with the timing connector unplugged,then the ECM has likely gone bad?And is it safe(for the engine) to drive with the timing connector unplugged?I'm about 20 miles from the nearest decent shop or parts store,and would very much like to not have it towed. Thanks again.

vwdave

Do the test like you would for a code 42. It could be a number of things. Ranging from a ECM (like mine) to a ESC module, wiring short and a bad PROM.

You can drive it, but it wont have any power and your SES light will be on because the connector is off.

flightform89

I have been using a haynes manual to try and locate the timing connector,but the pictures they use for the illustration are from a v-6 model.I appreciate you helping a fuel injection newbie out,so I hope this isn't the stupidest question-where is the thing?

vwdave

Its a black/tan wire running from the distributor to the computer, its somewhere in that track. I THINK its on the firewall near the distributor, on my car, its 6" off the computer cause that is where painless wiring puts it.

flightform89

I believe I found it.It is a black wire and a tan wire connection on the passenger side near the firewall.The illustration of the v-6 model had it next to the brake booster.I disconnected it but have the same problem>Having to pump the pedal to keep it from cutting off.I've read here that the ECM usally does not fail,but the panel on the hood bulge has been removed,so I guess water might promote an early ECM death.Of course,I've also read that the engine should run even with a bad ecm(I think I did,anyway),so I'm not sure where that leaves me.This felt like a progressive problem.A rapid one,but one that makes me think it's a part failure rather than a short.Thanks for the guidance.Of course,I may have just dissconected the wrong thing,but that was the only black wire/tan wire I found.

flightform89

Just realised that the ECM is inside the car,so the water theory is dumb.duh

razor

Are you getting any codes when this happens??? By the sounds of it you have found the correct wire to disconnect for the timing. Have you unplugged your MAF yet??? My 89 GTA did the same thing last summer without throwing any codes and it turned out to be a bad MAF relay. Unplug yours and see if the car idles smooth. You will not have the same throttle response as the car is not able to tell exactly how much air is being used but if its MAF related your idle will be better and will not stumble when the MAF is unplugged.

flightform89

well,it's amazing how a problem can motivate learning.I thought you had to have a tool to read codes,but I just jumped the two terminals,and only got the repeating #12 that says it was checking correctly.No other codes.I'm going to go out now and find and disconnect the maf relay like you suggested.Was your GTA undriveable with the bad relay still connected?Thanks.

razor

Don't disconnect the relay itself. Just unplug the MAF sensor thats in your air intake ducting by the radiator. The plug will be on the bottom of the MAF sensor. When my MAF relay went I was just out cruising the streets looking at cars when bam, it just started to die. It felt like something fuel related. It quit and then fired up after 5 minutes. I made it 3 more blocks and it quit again. The car would not idle or run. I unplugged the MAF sensor and it started right up and ran moderately smooth. Thats when I knew I had to start checking the MAF system.

razor

....double post....

flightform89

I wish I could buy you two guys a drink,or a cappachino,or whatever floats your boat.I just disconnected the maf sensor wire,and now it idles on it's own.It's a 100.00 bucks to get a tow where I'm at,and you just saved me that,razor.10 miles from the nearest convenience store,and I'm out of milk,dog food and almost 100 bucks.Hope I can pass the favor on somehow.Big thanks to you both.

razor

Hey I am happy it worked but now you have some diagnosing to do. There are 2 power relays for the MAF system. One is for the MAF sensor itself and the other is for the burnoff relay inside the MAF. Chances are and also hopefully one of these is to blame and not the sensor itself. The realys are found by the brake booster. There will be 3 relays all bolted to the same bracket directly infront of the brake booster. The outside ones are the MAF relay and the MAF burnoff relay. The center relay is for your headlights IIRC . Your fuel pump relay is also right beside this group of relays and while replacing them you should do the fuel pump relay as well. These relays are cheap and probably need changing anyway. The MAF relay and MAF burnoff relay are the same part# so you can try to switch them before you spend any money on relays to see if your car idles better. If its not the relays then you need to search the boards for a diagnosing schematics to verify if your MAF is bad or if its a supply voltage problem or something in the ECM. I still think it will just be the 2 MAF relays though.

flightform89

Good advice on the relays,too.I will definately replace all of them.The only engine compartment modification on this car that I know of is a SLP cold-air kit,so I'm also going to check to see if the screen has been removed,and if it is,if the maf wire is damaged.I also need to put a 180 degree thermostat in.I think the previous owner put a 160 degree opne in,and the only time I even get to 160 degrees is if I'm stuck in traffic.From what I understand,that means I'm in open-loop all the time.

flightform89

Just as a follow-up,I tell you-I LOVE this car.I looked hard for about two years trying to find my dream car,and it came out to be a 1989 formula.Once I had that figured out,It only took me a month to find a really good one.I bet I could have been swayed by a 1989 GTA or TA,though,if I had come across one.(I really like the irocs and z-28s,too).What a fantastic machine these 'birds are.Corvette sized right.This board is really great,too.I've been pouring over it ever since I decided on a third gen.This place is a limitless source of information.If I hadn't had this board to help figure this problem out,that 100 bucks would have only got me to a shop.Who knows what could have happened,then.

razor

Well as far as the 160 degree setting goes, it might be a little too low on a daily driver in colder temps. But I will say this though, just a simple thermostat change will not bring operating temp up. One of the biggest factors is the temp at which the 2 electric cooling fans enguage. On a stock tpi the primary fan enguages at roughly 220ish and the secondary fan comes on around 236ish depending on AC line pressure IIRC. If your car runs this cool there has been a modification to the fans somewhere. AFAIK there are 3 ways to do this. The first is obvious, just run direct power to the fans on a toggle switch. The second is to buy another temp sender that tells the ECM to turn the fans on earlier. Hypertech and others make this device. The third way is to change the fan settings to come on earlier by reprogramming the eprom in the ECM. I would venture a guess that you have the second or third of my suggestions as far as cooling goes. You need to figure out which ine first before you can go about addressing the problem. And just so ya know, some people will tell you the ECM will not go into closed loop. My 89 GTA has both fans enguaging at 175 and off at 165 with a 160 t-stat and always enters into closed loop every time. You can watch on the laptop with datamaster. It seems to go into closed loop right around 140. It just depends on the vehicle though as I know some people on here have had trouble.

flightform89

Well,my fan(s),come on if I just turn the ignition switch to the "on" position.I would guess that it might just be hard-wired to constant on.

razor

Yeah if your fans come on with the key in the run posistion and stay on, I would think they are directly wired. Either way it should be easy to fix which ever way you decide to go about it. I hope you get your car up and running soon and all the maf issues figured out. Have a good one! Jay

flightform89

Man,I got to the store for food for my animals and milk for my coffee,so I'm assuredly having a good day.What the hell good is a perfect sunday at home if your dogs are bitching at you because they have to eat saltines and you can't have your coffee the way you want it.Not to mention the prospect of a tow and shop fees.It's the middle of january and it's almost 70 degrees here today.Too good a day for all that.I'm looking forward to replacing everything tomorrow,too.Can't wait to do some more power driving.Especially since I won't have to wait for a shop to look for the problem,find it and fix it for me.All thanks to you and the superb board of thirdgen.org.