Hi Guys,

Ok after a good summer cruising last year I put the Firebird away as usual at the end of October for her winter hibernation, and also as usual I took her out at the end of January for a mid-winter warm up and check over.

Right, so I put the battery back in and fire her up. No problem, she leaps into life almost before my fingers turn the key and settles down to a fast idle. After 10 minute's she’s settled down to 650rpm and we set off for a run.

I stop at the shops after a very smooth run about 14 miles later for about 2 min. When I go to start the engine though it immediately starts to run rough and varies between 550 - 800rpm and almost stalling. Thinking that it’s the computer trying to get its bearings I carefully drive off and notice the car seems to be not firing on all cylinders. The more you put your foot down the worse it is. As I pull over and start to brake the car is trying to surge and buck slightly, and on pulling over resumes a very lumpy idle. I thought the best idea would be to get the car home ASAP so I went via the motorway and noticed under very light throttle at speed (50mph) the car surges and bucks lightly. Up to now the car never stalled but at one set of lights it cut completely under braking from about 5mph.
I had no problem re-starting it but it immediately resumed its 500-800rpm rough missing idle. At no point did the check engine light come on (except when it stopped which is normal) and the autobox worked fine. Once I got home I interrogated the ECM and only got the system check code (1 pause 2) I also pulled the plugs as I’m replacing them along with the distributor cap, rotor arm and plug leads in the following three months.
The plugs didn't show any signs of trouble, the normal light brownish grey although there was some light fluid (gas?) on all of the threads. I also removed the air filter, which I must admit to my own embarrassment was very dirty! The filter has been the only service item I have missed so far due to more pressing items to change on the car. (Excuse!)
Anyway not sure if that could be the cause of my problems. These symptoms did reveal themselves last summer briefly. Again I’d shut the engine down (running smooth) and then re-started it. The only difference being that the starter seemed to stick for a split second, then start and the rough running began. After a short space of time it started to run normally again and I thought nothing more of it. Don’t know if this is relevant but when I had the car M.O.T'd last September the tester said that it initially failed the emissions test (It never has before) even though the car had been running for 30min+. So he held the throttle open for a while because he suspected that it was still on cold start (engine rpm was at 650 though) After trying the test again it passed with no problems. What I find strange is that the car starts and runs fine and only starts it’s rough running after I park up for a while. After it runs rough, it just clears up and is fine again.
Like I said I’ve now got round to doing engine work now all my brake and fuel tank jobs have been done, so I’m replacing as much as possible. Unfortunately, the car’s now laid up until April so I’ve no way of testing any suggestions, but any ideas on what I can replace in there while I have it in bits for the next few months is much appreciated.

I'm not used to the Bird running like this as she's been faultless since I’ve had her, and want to get her back to 100% for April when I put it back on the road.

All the best guy’s

Speed.

 

sounds like maf, you got a spare kicking around?

 

If the car has been setting its got to be bad gas or even more probably you have deposits built up that have clogged 1 or more injectors. Gas has a tendancy to do this when setting for long periods.

 

Hi Guys,

I¡¦m pretty sure it¡¦s not the fuel, I only filled the tank in October and I¡¦ve got a Mazda that¡¦s got all the fuel from the Bird in it when I changed the fuel tank on the Bird (last Feb-Mar) and it runs fine nearly a year later!
As for the Injectors, well I¡¦m not sure you could be right there, but surely it would run rough all the time and not just when I stop and then restart?
I don¡¦t have a spare MAF though, this is England your lucky to find a Firebird here never mind a MAF for one! ƒº It¡¦s another possibility though that I¡¦ve got to look into. Something keeps telling me that its something to do with either the ignition or the cold start system, what ever I¡¦m pulling stuff off next week (plugs, leads, distributor cap, rotor arm etc) so I¡¦ll investigate more then.
Thanks for the suggestions though guy¡¦s I¡¦m open to all ideas ƒº

Speed.

 

A car will cruise fine with a bad injector, but wont idle and wont accelerate- exactly the symptoms you describe. I would strongly advise checking them. the gas in the tank may still be fine but the gas in the fuel line /injectors evaporated and left mineral deposits the block/clog the injectors- does this in motorcycle carb jets all the time when people let them sit for a few months without turning off the fuel supply and running the carb completely dry of fuel before storage. The injectors can dry out and leave the same deposit buildup.

 

Ah right I get ya, well I was thinking about replacing the injectors as a matter of course so I'll have a look at them next week when I have the Plenum off, thanks for the heads up Naed

Speed.

 

If its a 3.1 it doesn't have a MAF.

Injectors sounds like the best suggestion anyone has made so far. You can check them electrically fairly easily, just unplug the connector, and run the probes of a digital volt/ohmeter to the two contacts on the injector. The resistence should be about the same from one to another. The entire set should match up. Normally they usually pull 12-16, the measurement doesn't matter as much as how closely matched they are to each other. If you have one or more that are too far off from the rest, its safe to assume they've failed. Stay away from most over the counter fuel injector cleaners with the stock 3.1 injectors, they've been known to cause problems.

Unfortunately there are a lot of things that can cause the problems you're having, including EGR, fuel pump, fuel injectors, wiring, ECM, sensors, etc... The positive is that if it fails completely the ECM might tell you in the form of a code. If all else fails just keep driving it till it dies and it'll be easier to find then if its an intermittent issue.

 

Best injector fuel cleaner additive is STP. I would recommend trying that first if you can find it.

 

Seafoam is the best fuel system cleaner hands down.
Its really works.

It was made for the boating world and is now big in the bike world.
So many people have fixed a crappy runnin bike by just dumping that in their tank.

Its slowly making it way into the car world. Mostly only found at NAPA and is slowly makign its way into Canada.

It says oil and gas on the can but everyone just uses it for gas.
Though we confirmed from their reps that its safe for a wet clutch system.

 

Hi Guy¡¦s,

Thank¡¦s for that Idea Drew, I¡¦m on holiday next week so I¡¦ll be messing around changing the plugs and that anyway, so I'll have a go with testing the injectors. Must admit it¡¦s not the first thing I would have suspected, but makes sense seeing how I only drive the car 700 miles or so each year. I had a look down the car supply shop today and have got some STP injector cleaner (they never heard of seafoam this is England you know AKA the back water of nowhere!) ƒº
I¡¦m also going to invest in a fuel pressure tester to check the pumps output if I can get my hands on one. Does anyone know the thread size of the schrader valve so I can get the right size tester, or is it a universal fitting?

Thanks for the help guy¡¦s Speed