JBL930

Could it be over boosting and protomotive have some sort of over boost protection? I know this is exactly what the motronic ECU does when it isn't happy, it pulls fine and then stutters and misfires. My car was only doing it when really cold, denser air etc and the map wasn't compensating properly. I know yours will be a different set up, but thought it might be worth a thought?

mikelambert1987

Ahh thanks for the info on the fuel run off. The over boost thing is a definite possibility. Here is my question. My boost gauge in the dash is terrible and inaccurate and reads around 1.1 bar. We know it isn't running that high in reality because we hooked a gauge up to the car and ran it into the cockpit and checked the real boost while driving and it never peaked up over 14 psi which made sense for the spring put in it. I dont know if i have the mototronic or anything like that as mine is an 88 with cis. I have watched my mechanic and he uses what looks like an allen wrench to adjust the mixture maybe etc.?

mikelambert1987

also that is exactly what mine sounds like with a shudder and what sounds like a misfire/backfire/shudder

mikelambert1987

So with a cis engine management what can be done to fix that map mixture?

Mike

JBL930

With CIS everything is mechanical, no ECU. I didn't know whether, with you saying it was a protomotive car, it had been played with in anyway? You do have overboost protection, i believe it cuts the fuel pumps. It could be acting up so worth a check, if it's not smoking it won't be over fueling which would point to WUR issues. I would get your WUR sent off to Brian leask anyway and have it made adjustable, you can then acurately adjust all of your fueling, cold, warm, cruise, enrichment and enrichment threshold. May be worth getting his RPM solenoid too to delay enrichment further to iron out the rich mid range CIS gives. If you've gone through all of the ignition stuff and all is in order it is most likely your overboost switch, the CDI box "usually" works or it doesn't, it should hum gently with the ignition on

Mark Houghton

All good suggestions. There is a huge thread over on Pelican regarding all the tricks and some theories on fuel management with CIS systems...ranging from adjustable WUR's coupled with boost enrichment delay, to aftermarket programmable frequency valve controllers tied into the Lambda system.

Regarding your persistent stutter (well...not yours, your engine's!), you can pull the single wire off that overboost switch (and then ground it) to take it out of the equation. But be aware that you would no longer have that protection if you ever did over-boost. That simple boost switch is tied into the infamous "yellow relay" in the rear relay tray, which shuts down the fuel in the event of an overboost situation. It too could be giving you fits, but ordinarily when it starts to go you would experience either a no-start or a suddendly-dies situation.

You can rule both of those (the sensor and relay) by forcing the fuel pumps to run all the time regardless of the air flow sensor plate deflection. Pull the blue electrical connection plug from the top-back of the fuel head (it connects to a micro switch operated by the control arm deflecting when air flows over it). The pumps should start immediately with the ignition key on. Start the car and drive it. If it still stutters, next pull the boost sensor switch wire and ground it. Test drive again. If still stuttering, pull the yellow relay and short from pin socket 87 to ground (thus bypassing the relay function). Test drive again and if still stuttering, it's not because your fuel flow is stopping (unless you also have issues with the fuse or the 2 relays up front in the fuse box).

mikelambert1987

Ok there is a definite hum when the key is turned. So will start with the blue electrical connection thats at the top of the fuel head. The fuel head is located ? if that doesnt work I will do the boost sensor one and ground it etc. Thanks for all the great advice guys. I will hopefully get this thing settled down and working 100 percent before summers over

A930Rocket

See pix attachet..

911rudy

I found that with the engine running I could pull one of the fuel pump relays in the front trunk and if the other one is good the engine will still run. If the first one doesn't shut it down replace it in the socket and then pull the second.