I’ve searched the archives and haven’t found a definitive answer so I’m asking for advice.
My ‘86 SE with 45000 miles has a hard starting issue. Before I purchased it, the car had been sitting for 10 years. When I took possession l replaced the brake system completely, new cap, wire, plugs, distributors & ICM. It has a new fuel tank, pump, sending unit, strainer, filter, lines etc. Timing has been set correctly (with the jumper in place ).
The fuel pump primes when the key is turned and the system hold about 40 psi when stopped.
When cranking, the car takes several attempts to get it to fire. When it finally starts you have to play with the throttle to keep the car running. When warm, the car cranks and starts easier but it’s not a as easy as my ‘86 GT with 106,000 miles.
I’m thinking I have 1 or more faulty injectors. I have a new set of 6, 15# injectors I’m thinking of installing. Before I get into this, is there something else I should look at ?
Mike, I'd make sure the Manifold Air Temperature and the Coolant Temperature Sensors are both reporting the correct temperature to the ECU. If either one or both are reporting erroneous high temperatures, the air/gas mixture won't be rich enough for a cold start.
If they check out okay, make sure the cold start injector switch and the cold start injector are doing their job... but I would suspect one or both of those sensors first.
Mike, I'd make sure the Manifold Air Temperature and the Coolant Temperature Sensors are both reporting the correct temperature to the ECU. If either one or both are reporting erroneous high temperatures, the air/gas mixture won't be rich enough for a cold start.
If they check out okay, make sure the cold start injector switch and the cold start injector are doing their job... but I would suspect one or both of those sensors first.
MAT and Coolant temp sensors appear to be working fine. The car is starts easier when warm but you have to play with the throttle. If you give it too much gas, it stumbles and dies if you feed the gas in slowly until it reaches 17-1800 rpm then it takes off and drives like it just came off the assembly line.
There are no codes from the ECU other than the 1-2 code confirming the ECU is o.k.
I have to say, I’m stumped. I’m wondering if the Idle Air Control is faulty or out of adjustment. I haven’t replaced fuel injectors yet but I’m not discounting that…
[This message has been edited by Mike in Sydney (edited 08-22-2024).]
The fuel pump primes when the key is turned and the system hold about 40 psi when stopped.
How long does it hold that pressure when the fuel pump stops?
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Originally posted by Mike in Sydney:
If you give it too much gas, it stumbles and dies if you feed the gas in slowly until it reaches 17-1800 rpm then it takes off and drives like it just came off the assembly line.
I’m wondering if the Idle Air Control is faulty or out of adjustment.
IMO, the IAC would have nothing to do with those issues mentioned above.
My next guess (if the fuel pressure isn't dropping too quickly) would be the MAP sensor. It's been suggested many times over the years here to temporarily unplug the MAP sensor (I'm assuming the reference is to the electrical connection, not the vacuum line) and see if the engine runs any better in a limp mode default setting for the MAP. That test has never worked for me, as my engine(s) wouldn't run at all with the MAP unplugged... but try it and see what happens.
[This message has been edited by Patrick (edited 08-22-2024).]
Car has a new fuel, tank, pump, sender, etc. I can hear the pump prime and continue to run when the car is started. I need to check the residual pressure and how long it takes to leak down. Ive also installed a new MAP sensor. I’ll try unplugging it to see if there is any change. It could be faulty out of the box.
I have to admit, I’m stumped. It doesn’t act like a typical vacuum leak because after it it warm the idle drops to 8-900 when it is in neutral. Doesn’t like to hold an idle while in gear. Sometimes it idles higher but a tap on the throttle drops it down. When cold, putting it in gear is an issue. It dies unless you give it some throttle.
Car has a new fuel, tank, pump, sender, etc. I can hear the pump prime and continue to run when the car is started. I need to check the residual pressure and how long it takes to leak down. Ive also installed a new MAP sensor. I’ll try unplugging it to see if there is any change. It could be faulty out of the box.
I have to admit, I’m stumped. It doesn’t act like a typical vacuum leak because after it it warm the idle drops to 8-900 when it is in neutral. Doesn’t like to hold an idle while in gear. Sometimes it idles higher but a tap on the throttle drops it down. When cold, putting it in gear is an issue. It dies unless you give it some throttle.
I’m wondering if the Idle Air Control is faulty or out of adjustment. I haven’t replaced fuel injectors yet but I’m not discounting that…
Well, it ain’t the IAC. I replaced it and there was no change.
I had the distributor replaced sometime back. The old one was badly rusted from sitting. (I purchased the car unseen and had my mechanic in the U.S. do some work to get it ready for shipment back home to Oz.). I’m now wondering if the mechanic may not have ensured number 1 was at TDC when he installed it. Number 1 position on the distributor appears to be further clockwise (3 o’clock vs. 1 o’clock) than on my GTs .
I had the distributor replaced sometime back. I’m now wondering if the mechanic may not have ensured number 1 was at TDC when he installed it. Number 1 position on the distributor appears to be further clockwise (3 o’clock vs. 1 o’clock) than on my GTs.
...the cap position can be anywhere you wish to orient it... as long as the rotor is pointing to the terminal used for #1... and the piston is at the top of the compression stroke for cylinder #1.
Well, it ain’t the IAC. I replaced it and there was no change.
I had the distributor replaced sometime back. The old one was badly rusted from sitting. (I purchased the car unseen and had my mechanic in the U.S. do some work to get it ready for shipment back home to Oz.). I’m now wondering if the mechanic may not have ensured number 1 was at TDC when he installed it. Number 1 position on the distributor appears to be further clockwise (3 o’clock vs. 1 o’clock) than on my GTs .
Yeah, well that ain’t the problem, either. Doubled checked it after getting home from church. Same result. S#$& !
Started to replace the injectors and realised I didn’t have the proper Torx bit to remove the throttle body. Running out of time before I leave for Oz so I’ll drop it at the mechanic’s place tomorrow and see it he can sort it out.
BTW, I tried unplugging the MAP so it would run in limp mode. No joy.
Well, now that I'm back in Oz, the problem and mystery has been solved and resolved. The car, however, is still in North Carolina. (Pictures below of my $1000.00 Fiero with 55K miles)
According to the mechanic, there were two vacuum leaks that were intermittent. That caused the hard starting. When coupled with a faulty new fuel pump that I had installed last year, the problem was exacerbated. The pump would prime but after the car started, low fuel pressure would cause the stumbling under load.
Moral of this story: Always double-check the obvious things and remember that things may be faulty right out of the box.
[This message has been edited by Mike in Sydney (edited 09-03-2024).]
When coupled with a faulty new fuel pump that I had installed last year, the problem was exacerbated. The pump would prime but after the car started, low fuel pressure would cause the stumbling under load.
Mike, after reviewing this thread, I now realize you never responded to my fuel pressure question. Next time I'll be a bit more dogged when asking for info. Anyway, glad to hear the issue has been resolved.
quote
Originally posted by Mike in Sydney:
The fuel pump primes when the key is turned and the system hold about 40 psi when stopped.
