Missing when cold
 

I had a cold starting issue here :https://www.scoobynet.com/general-te...-problems.html which seems to be ok now, however i still have a problem with the car missing when cold, it normally does it when left to get cold for a few hours, not overnight? so for instance when i leave work, or like just now when i went out to lunch.

I have replaced the CTS, the lambda is new, i have tubular headers now fitted, an uprated fuel pump and standard pressure regulator, standard injectors and a Z4 ecu, the car is a 1993 WRX.

I get no error codes on the ecu.

I have a coil pack to try, but does anyone have any opinions as to what might be causing this?

Thanks for any input, right now i could drive the car off the end of the linkspan and let it float out to sea!!!

Yours Hopefully

Dave

Sounds like an electrical issue, when did you last change the plugs buddy???

Sorry forgot to mention i did the plugs recently too.

I had trouble with the plug nearest the passenger so ended up bolting the coilpack on at an angle to get it to the garage, thats why i have a coilpack ready to try incase it cracked it somehow?

Dave :(

Test the voltages of the various sensors?
The uprated fuel pump possibly over powering the standard fpr?
MAF?

Could well be a coil, i would fit a new one on the suspect cylinder and cold start test it to see if the fault occurs again. If it does start trying it with each other cylinder to see if the fault is infact on another cylinder.
Matt.

What sensors would you suggest?

I unplugged the MAF and it died stright away.

I also have a crank sensor waiting to go on if the coil pcak doesn't fix it.

I did wonder about the standard FPR would this be possible ?

Dave

Yeah i'll try it on each plug in turn.

I'm sure it just flat wouldn't start if it was the crank sensor. The ecu needs crank signal for timing of spark, cam, and fueling. It would just crank over and never start if it was a crank sensor. Then again stranger things have happened at sea.

Yeah i bought it just incase really, thats why i haven't tried fitting it yet!

I'm going to try the coilpack tonight when i get in i think!

Crank sensor
Maf sensor
Coolant temp sensor
And all the associated wiring

The standard fpr ,unless changed, is 17 years old so with a brand new pump it could be having trouble coping.

Changed the coil pack last night, it looked like it wasn't flush against the head due to the bolt being cross threaded, there was also alot of green deposits on the contact end of the coil pack i dont know if that indicates anything, perhaps arcing? I wont know if its fixed till either lunch or Home time!

Green deposits mean water has got in there and caused corrosion! Probably due to the fact the coil wasn't flush allowing a way for water to get in between the coil and spark plug contact. This is most probably the cause. Clean it up with some contact spray, sort the thread, new coil on and i'm fairly sure it will be back to it's old self my fruity!!

I dont want to drive it later in case it's made no difference!!!

Fingers crossed!

And toes!

Sorry for posting up oxygen sensor on your other thread. I should of read it properly then i would of seen youhad changed it :o. It does sound like water has got into the coil pack as mentioned above especially with the damp weather. Hope you get it sorted. :thumb:

crank sensors can cause a miss under boost so i dont see why it couldnt cause a cold start miss ??

First test was a sucsess! Drove home last night and no missing, dont want to count my chickens just yet, i'll see how it goes tonight when i leave too, but so far so good!!

Cheers for all the comments chaps!

Dave :)

Nope still missing / spluttering / back firing when cold, for instance after work. Dont know what else to check :(

To recap i have replaced the CTS, the lambda is new, i have tubular headers now fitted, an uprated fuel pump and standard pressure regulator, replaced suspected coilpack with new one, standard injectors and a Z4 ecu, the car is a 1993 WRX.

I do however believe the new headers are blowing somewhere, could it may be causing a problem if this is the case? perhaps with the lambda sensor reading?

Dave

Ok so we know the spark is ok, it could be the exhaust leak- where is it leaking from?? also have you got anyway of measuring fuel pressure?? i.e with a pressure gauge.

I am going to get under the car tomorrow and see if i can see anything!

a garage would have to test the fuel pressure. Do you think it could the fpr not working correctly?

have you done compression test yet had exactly the same on my94 sti turned out to be piston ring. its worth the hour it takes to do just to rule out worst case .

james

James is right, as you'll have to take it to a garage to get the fuel pressure checked, you might aswell have the compression tested too. To be honest its starting to seem like this may be fuel related. If you rev the engine does the misfire seem to go away???

Manifold to uppipe is leaking , i dont think there is even a gasket in there!

I'll get that sorted and see if its any better afterwards. I'll do a compression test and then get the garage to check the fuel pressure.

cheers for your comments

Dave

To answer the reving question, i dont really rev it when it happens as the engine is still cold, i did rev it a bit the other day as i was so annoyed with it and i think it still missed a little bit. It still clears when the engine is warm!

Dave

Where do you buy your fuel from.

sometimes BP, sometimes Sainsburys.

Dave

A leaking gasket could cause a misfire, if its blowing as bad as you say then i would expect it to be running like a bag of cat poo all of the time. The gasket is going to need changing anyway, so get that sorted and see how she goes.

I'll let you know what happens when its done mate!

The reason i ask is i had a similar problem when running on tesco fuel but swaped to shell and it sorted it. :thumb: