When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi, a couple months a ago my car started to idle weird. The car's idle rises and then drops and it continues to do so over and over. I have the venturi delete hoses and vacuum hoses from lindsey racing installed and I've checked for leaks. The ICV has been deleted. The TPS seems to be in the right position as it clicks as soon as the throttle is touched. When I unplug the TPS cable and run the car it no longer cycles and idles around 2300RPM. Not sure what to check next, any help appreciated.
This sounds like a vacuum leak I once had at the J-boot. How did you check for vacuum leaks? Did you just do a visual or did you actually pressurize the lines? If you are positive you don’t have a vacuum leak I’d be looking at the tps as you stated the idle hunting stopped with it unplugged, maybe swap with a known good one to check.
Check The "O" Ring on the Idle Adjustment Screw" Make sure its still in good shape... The First thing that is E-Z Is Spray some Starting Fliud around the engine bay in Various areas and see if the Idle changes.. Last fall I did A Timing belt on my Street car and was inspecting things as I re-assembled.. I noticed and SMALL Teeeeny-Tiny crack in the intake boot (IC-to Mainifold) and with a little pressure was able to see that it had fully cracked through.. The car always ran prefect and had good boost so I never had any reason to look.. BUT, after putting a new boot on and taking it for a rip down the street... That boot was costing me about 30hp.... (was venting on boost)…. Also make sure the Diagphram is seated properly in your BOV (if its stock) … Had one "Fold over" one time as well..
I've pressurized the system and used soapy water to find leaks a couple weeks a ago. There was some small ones and I fixed them. Unfortunately I don't have a spare TPS to swap out. I checked my BOV and the diaphragm is seated. When I pulled the idle adjustment screw out the o-ring crumbled into pieces (see picture). I'll get a new one but could this be the cause? Thanks.
I put on an o-ring that I found laying on the bolt. I then plugged the top of the idle adjustment hole with my thumb while the car was running and the idle continued to rise and fall.
Hmmm well there are other things that can cause that. My GOTO has always been the Bosh fuel injection handbook, you need to look at all the components that make the system. The O2 sensor might be intermittent, It might be reading temp intermittently, The venturi delete is an ok thing because Porsche did it themselves later on, however Im not a firm believer in ISV Delete...I think the only time I would do that is if I knew the engine was in perfect order. I have a Standalone on my track-car with no ISV but I know the engine is Tight because I just built it. But that's a totally updated system that I can look at thing with my laptop as well.. Get the book, Read it through, Its always steered me in the right direction,
Did you mean ISV or ICV? I still have the ISV but deleted the ICV. What do the both of them do by the way? I certainly look into getting a copy.
????
Not certain what you mean by that, on our cars there is only one valve that controls idle regardless if you call it an “idle control valve” (ICV) or an “idle stabalilizing valve” (ISV). If you deleted it your idle will hunt high and low until the engine is up to temperature.
Not certain what you mean by that, on our cars there is only one valve that controls idle regardless if you call it an “idle control valve” (ICV) or an “idle stabalilizing valve” (ISV). If you deleted it your idle will hunt high and low until the engine is up to temperature.
Sorry I may be mixing up the names but I deleted the small circular, yellow coloured (thing) that has three vacuum hoses running to it.
Sorry I may be mixing up the names but I deleted the small circular, yellow coloured (thing) that has three vacuum hoses running to it.
Three vacuum hoses...mmm, can you post a photo?
This is the idle control valve, it’s positioned under the intake and has two vacuum hoses running to it and an electrical connector. Like I stated, if you deleted this your idle will hunt high and low and possibly stall when the engine is cold.
Never Deleted a Cycling Valve with a Bosh System. But Thinking about it, You must have a direct line running from that 17mm Banjo Direct to the Wastegate.. If youre running the Stock J Boot Make sure where that "Other" hose goes is completely sealed.. The J boot itself is also "Suspect" Because ANY leak there is "Un-metered" Air and the Idle control Valve will try to compensate and it will "Hunt" for idle... The Idle control Valve itself could be sticking, Its basically a Throttle plate bypass. Anyhow hard to diagnose without putting my hands on it... Try the starting fluid trick,,, Then wiggle the wires around the idle control Valve.. Other than that try cleaning it and if youre using the stock barn door air meter look up some threads related to carbon tracks and cleaning.
Good Luck... Gotta get to bed now, leaving for Hershey at 2 am... (5 hr drive) keep us posted
Never Deleted a Cycling Valve with a Bosh System. But Thinking about it, You must have a direct line running from that 17mm Banjo Direct to the Wastegate.. If youre running the Stock J Boot Make sure where that "Other" hose goes is completely sealed.. The J boot itself is also "Suspect" Because ANY leak there is "Un-metered" Air and the Idle control Valve will try to compensate and it will "Hunt" for idle... The Idle control Valve itself could be sticking, Its basically a Throttle plate bypass. Anyhow hard to diagnose without putting my hands on it... Try the starting fluid trick,,, Then wiggle the wires around the idle control Valve.. Other than that try cleaning it and if youre using the stock barn door air meter look up some threads related to carbon tracks and cleaning.
Good Luck... Gotta get to bed now, leaving for Hershey at 2 am... (5 hr drive) keep us posted
I removed the j-boot this afternoon, cleaned it and made sure it was all in good shape. I have the hole plugged with a snug fitting bolt and a hose clamp. Everything seemed to be in good shape. I also tried wiggling the wire on the idle control valve, didn’t seem to do anything. At some point the PO must have removed the mount for it because I have it just sitting there under the manifold. The wire is somewhat bent and under pressure from the Venturi hoses. It’s not in the best condition but there’s no exposed wire. I’ll go buy some starter fluid in the next couple day and try that, thanks.
04-17-2019, 10:37 PM
Rising and Falling Idle
