BLBncsu

Hey all. My 97 Formula M6 with 123k has been running good but the issue is after driving the car/warming it up and then stopping someplace and letting it rest/cool for 45min-1hr; once I go to restart it, the car runs horrible for about 5 minutes or 3 miles. It barely will start, if at all, and when its under load the car hesitates, bucks, or dies.
When I push the clutch in though and rev the engine it seems to rev/run fine.
When its started cold (i.e. in the morning) it runs perfect though. There are no SES lights coming on so I'm a bit stumped on where to begin looking.
Thanks!

Guest47904

Sounds as though you may be having a "vapor" issue. Like the fuel is boiling away at some point in the line and leaving a large vapor "hole" in the supply of fuel. Once it runs long enough to get the vapors through and into a good supply of fuel, it runs ok.

You could do an easy experiment with the schrader valve, some fuel proof hose and the fuel pump prime connector to prove it out.

BLBncsu

What would be the potential cause of this, I haven't heard of this before?
I assume your experiment involves seeing if fuel would actual come out of the valve versus vapors? Not entirely sure either what you mean with the fuel pump prime connector or the exact setup of this test.

I'm open to try anything or look at any other options. Thanks.

bw_hunter

I think it could also be a leaky injector or injectors. On a cold engine you need a little more fuel to get it running right so a leaky one would't be noticed too much. Once hot, the extra rich mixture will cause hard starting and rough running...until it clears itself out, like when you would flood a carbed engine.

Do you have to crank it a bit when starting the engine cold?

BLBncsu

Thanks for that idea also.
It does require just a bit more effort than usual to crank it and start it even when cold.

How would one go about checking if the injectors are leaking and how difficult would that be?

bw_hunter

It's not terribly difficult. What you do is remove the 4 bolts securing the fuel rail to the intake manifold. These bolts are weak so be careful. Anyway, after removing those bolts, lift the rail off the manifold and have an assistant turn the ignition to 'on' but not start. If you fuel dripping from any of the injectors, it's leaking and needs to be cleaned or replaced. No fuel dripping indicates this isn't the problem.

Do take care...turning the engine to 'start' will cause fuel to be sprayed from the injectors and could create a fire hazard.

Good luck!

BLBncsu

Thanks for the response.
An update though: I had my car scanned even though it wasn't throwing a SES light and had the these two stored: P0100 & P0123
I'm wondering if the Throttle position sensor (P0123) would also be causing this issue, although I don't understand why it wouldn't be throwing a SES light and only occuring once the car is warmed up for those 5 minutes after a warm-start. I may try to check its voltage and if its reading right.

BLBncsu

Hey All! I still need some help with this issue.
So the problem still occurs where after letting the car sit from driving for 30-60 min and refiring it runs horrible for the first 5 minutes under load. I can hold the throttle in one spot with no load and the RPM's will vary some. After about 5 min its all good again and seems to run just fine (good idle, no high-end misses).
I finally got it to also just throw a P0300 (random misfire) code. The two codes stored in my previous post were stored also.
I'm stumped on where to begin before I am forced to have a mechanic dig into it all. Thanks.

Kevin Blown 95 TA

I'd take a look at the plugs and see if there is a clue what's going on there. Also, it's valuable to be able to log some data onto a laptop if you have a friend that has the cable & software. Maybe you have a sensor that is out of range or not functioning correctly. Maybe the code reader you are using lets you look at streaming data - that would be helpful, too.

95zsean

Opti........

BLBncsu

Well I don't have any access to a scan tool to check streaming data so I took it to a shop to do that. So far they are having a hard time figuring it out also besides showing a cylinder 7 misfire and that the computer is seeing one thing but the car is doing another.
I'm hoping for some more definitive results but not too confident, at which point I'll start pulling and looking at the easy parts I guess before jumping to the opti. She's already left me stuck once in a parking lot so need this resolved quick.

Injuneer

P0100 is a problem with the MAF sensor. The reading is static. This is not an unusual issue with the 97's for some reason. Pull the harness connector off the MAF sensor and key on/engine off check the voltage between the pink wire and the blakc/white wire - should be 12V. If you don't have 12V, its not unusual to have a break somewhere in the harness on the pink wire.

If you have 12V, first check the pins in the connector for damage. If they are OK, borrow a known healthy MAF sensor and see if things improve.

P0123 is a problem with the TPS sensor reading over 4.9V. With key on, engine off, check the voltage between the gray wire and the black wire - should be 5V. Then check the voltage between the dark blue wire and the black wire. Closed throttle reading should be in the range of 0.20 - 0.90V. Slowly rotate the throttle blades to full open. The voltage should rise smoothly, with no spikes or dropouts, to about 4V above the closed throttle reading. Under no circumstances should the voltage exceed 4.9V.

As far as the hard start, when you go to start it, put the accel pedal on the floor BEFORE you turn the key to "start". That puts the PCM in "clear flood" mode. Then try and start the engine, holding the pedal on the floor. If it starts easier, its pointing to leaking injector(s).

brandons94lt1

My car was just having a very similar issue, except it wouldn't spit and sputter under any condition except sitting in traffic in the heat. I was worried that the problem was something that would take fkreever to resolve, it turned out to be a corroded ground strap was fixing to break, and it acted up in the heat because high temps make wiring problems worse. I was lucky there, but them after fixing it my ac wont come on. That's another thread, grrrrrrrrrr.

BLBncsu

Did previsouly check the MAF, all looks good there.
Also did a voltage test as stated on the TPS and it too looked good, but probably worth a second look at this point.

Where are all the ground straps located at?

The shop says they aren't really seeing anything specific that is an obvious fault after spending a few days with it. The water pump (3rd one) is leaking again a bit (after about 2.5 years) onto the opti. Cylinder 7 is misfiring. The fuel pump/module is also occasionally not priming the system upon startup with enough pressure. The problem is somewhat intermittent and hard to pin-point. Bit of a lose, definetly not spending a ton to get it all fixed at a shop.

Injuneer

But they've found two (now three) trouble codes, and apparently have checked the fuel pump to determine that it is not consistantly putting out the correct pressure. How can you (or they) say "they aren't really seeing anything specific"? Look at Speedy's original post - overheating fuel pump could explain it. MAF problems could explain it. But it appears you'd rather just ignore those problems.

I don't get it???????