928 Rough Idle

[tfjoneser]

Hey Guys, This is my first post to the forum and need your help.

I have a 79 Euro and am trying to get it road worthy again. I have replaced the fuel Pump and the plugs wires, cap and button and can get it to start.

When it does start it runs very rough and can barely keep it running and wont accelerate at all, if you touch the gas it stalls out.

I have found that I can keep the car running by manually pushing down slightly in the throttle body on the plunger. When I do that it runs pretty smooth at idle. Any idea what could be causing this non/rough idle condition.


Thanks,

[AirtekHVAC]

I had the same issues starting out.....kept playing and tinkering with the adjustments, removed the little filters from the CIS....

Read my thread and see if something in it helps ya!

It's alive!!!!!

[MPDano]

Yeah, sounds like your A/F is off. Get that long 3mm allen and make very small adjustments.

[Danglerb]

Run some fresh fuel through it with some Techron additive added.

If you are just starting out after its sat for some time, I would redo the vacuum lines and check all the pressures etc. in the fuel system prior to making any adjustments.

Rough idle, runs ok otherwise sounds like an air leak to me.

[MPDano]

Mike, he's pushing down on the plunger. It's A/F.

[steve322s]

Originally Posted by MPDano

Mike, he's pushing down on the plunger. It's A/F.

because he is pushing down the plunger it is more likely he has incorrect fuel pressure. Could be vac leaks too, as well as plugged ports on throttle body, I had at least 5 plugged. plunger works off fuel pressure the higher the pressure the less it opens and the lower the fuel pressure the more it opens.

yes you could adjust A/F in this case but not the correct thing to do unless you have checked pressures and they are on.

if it doesn't respond to the pedal then your fuel pressure is too high

[Danglerb]

Originally Posted by MPDano

Mike, he's pushing down on the plunger. It's A/F.

I wasn't sure since he said "I was pushing down the plunger in the throttle body", but how often are these cars tuned too lean and its not a WUR issue?

[tfjoneser]

Thanks for the responses, is there a way to adjust the fuel pressure if it is too high?

[steve322s]

you will need fuel pressure gages, you can get an inexpensive set at harbor freight. search cis or k jetronic. to find examples of testing and settings

[MPDano]

Originally Posted by steve322s

you will need fuel pressure gages, you can get an inexpensive set at harbor freight. search cis or k jetronic. to find examples of testing and settings

I think we all went through thrying to find CIS Gauges at HF, they didn't have any with teh proper adapters. I can't remember where I bought mine, but for the life of me and my messy garage, I can't find my set anywhere. But I do know I bought online and not at HF.

[steve322s]

Originally Posted by MPDano

I think we all went through thrying to find CIS Gauges at HF, they didn't have any with teh proper adapters. I can't remember where I bought mine, but for the life of me and my messy garage, I can't find my set anywhere. But I do know I bought online and not at HF.

I bought my set at HF 120 bucks worked great and have all the correct connections. this is in NY I don't know about other states.

Master Fuel Injection Pressure Test Kit

[Danglerb]

Dano, you bought your's from JC Whitney didn't you?

CIS, aka Kjet, 101

[MPDano]

Yup, Hoffman brand from JCWhitney. Funny, haven't been able to find it in over a year too. Thanks for the link, now i know it's in a cardboard box.

CIS, aka Kjet, 101

[steve322s]

^^^^ looks like the same set I got from HB less the nice plastic case, How much was that kit?

[MPDano]

Loks like JC no longer carries it. you can google the model number and get a few vendors that carry it but with a plastic case.

Hoffman TU-447P Fuel Injection Pressure Tester

Looks like around $100-120