22 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHRough idle, after new exhaust and airfilter
Leading reported evidence
Replace gas cap
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Performed · outcome unconfirmed
Wouldn't you know, changed gas cap with a new one, reset battery and my car runs good as new.
Leading evidence: 'Replace gas cap' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Clean mass air flow sensor' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Clean throttle body and maf sensor today, - update
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Suggestion · Original poster
I will clean throttle body and MAF sensor today, - update on that will follow
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
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Outcome without a verified action link
But no difference, stil same rough "rolling" idle.
Hi
2 weeks ago i swap out the old rusty exhaust with a new from fabspeed, also i put on open power filters from fabspeed.
i fell like the car has lost power, and it has a rough idle. and i have a CEL for P1128 and P1130. (O2 sensors are brand new.)
When i take the car to the highway and give it some hard pulls, the idle will get just fine, and the engine runs smooth. If i let the car cool off, the problem will turn back.
Even if i drive slowly thorug trafik and the engine gets up to temperature, the idle wont get better, unless i give some hard pulls on the highway.
any experiences to share ?
Your double posts are confusing. In your other post you said " 2 weeks ago i got new fabspeed cats and muflers, new 02 sensors and new carbon airfilter intake. All installed."
Now in this one you say " 2 weeks ago i swap out the old rusty exhaust with a new from fabspeed, also i put on open power filters from fabspeed"
Which is it? Or do those things mean the same thing? I would suggest putting the stock air box back on as it is well known aftermarket filters cause these types of problems, especially related to the MAF sensor. Clean the MAF sensor with MAF cleaner. After that, clear the codes and reset the DME by disconnecting the negative battery lead. With new O2 sensors you need to remap the DME so new values can be set based on feedback from the new O2 sensors. You have to approach the problem step by step. You need to backtrack what you have done...is it the new air intake, MAF sensor, new O2 sensors, what type of O2 sensors, did you get them plugged in the right order?
i have testet the oilfiller tuper afterward, and when a take of the cap, the idle gets even worse, so i guess the oil filler tube is ok. But i have not checked the vacum line
Okay new Update
i put the oem air filter back on, but no real difference to feel.
idle is still rough and around 750 rpm to 850.
i did notice that the air pump didn't run, can that trick the o2 sensors ?
se o2 readings in picture
Did you clean the MAF sensor? Did you clear all the codes? Did you reset the DME? The DME needs feedback from the MAF sensor and O2 sensors to run right. So you need to get it set back to base values and then let it adapt. Is the idle hunting when it is running poorly at idle? The SAI pump not running will throw a separate code. But it does have it's purpose, pumping air into the exhaust system at startup to light up the cats faster while keeping the air/fuel mixture at a richer state, so that will affect the O2 sensor readings at startup. It's a balanced and complicated loop at startup until the engine reaches normal operating temperature.
No I didn't clean the maf sensors. Wil try that tomorrow.
all codes cleared with bosh testing computer via OBD2 port
how do I reset the DME? Do I need to pull the power from battery, or is there an easy way?
TB - Throttle Body
Was working on a fellow forum members 99' and he didnt have the throttle cable correctly in place, caused a whole lot of issues so thought i'd ask just in case.
RE battery 5 minutes would be heaps - others can confirm/might have a more specific time
I will clean throttle body and MAF sensor today, - update on that will follow
My MAF i showing 6,25-6,50 on the bosch tester when idle. i gues this number should be lower, and constantly, not jumping up and down.
Update!
Cleaned out throttlebody and MAF sensor with MAF clean, took the power from the batteri for 5-10 min, drove it for 20 mins round town (slow trafik)
But no difference, stil same rough "rolling" idle.
any moore ideas?
btw. O2 sensors are new but not OEM, could these aftermarket sensors be the reason?
A hunting idle is often caused by the Idle Control Valve (ICV) which is on the TB. You have to remove it and clean it out. Yes, our cars are very particular when it comes to the O2 sensors. What aftermarket ones did you put in?
Okay time for updates
stil I got a "rolling" idle' jumping up and down from 750 - 900 ( with ac on) - on cold start up, it's good for about a minute.
here is more info
1. o2 sensors are bosh sensors matched for oem part number
2. MAF and TB is cleaned
3. Exhaust system is is nice and tight - no visual or audible leaks.
4. Battery has been disconnected
5. All Intake vacum tubes has been sprayed with start spray - no engine response, so no leaks
5. Smoke detector test shows high HC values around 200-250, wich can indicate lean mixture. 02 numbers are high too
6. Spark plugs has been replaced- just to be safe
im pretty much now in very deep and my knowledge, what to do next, is running out.
remember it all started with new fabspeed exhaust, o2 sensors and air intake, I don't blame the new parts, but something happened
any more good advises?
Air oil separator, does exactly as the name suggests.
Located at the back/rear left of the engine.
Can be replaced in two ways:
1. Remove the left side intake
2. Drop gearbox and get to it from the back
Either way big big job, not an expensive part though.
I had a somewhat similar problem - rough idle, hard starts and CEL for air check valve. While I didn't do the upgrades you have, I did have a bad o-ring on my gas cap. Wouldn't you know, changed gas cap with a new one, reset battery and my car runs good as new. No problems for weeks.
Turns out the internal vacuum seal in the car can run afoul just from minor leaks in gas cap. Once that happens car wont run smooth until it's fixed. Id check that and see what happens
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