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First of all, I would like to apologize for the long winded post.
A little background...My father purchased a 93 R1 back in April. The car has 39k original miles and is in great physical shape, however, it has been sitting for quite a while. The original owner passed away and it has spent a lot of time sitting in their garage in recent years. It has only seen about 600 miles in the past 7 years or so. The car was not actually for sale, but we heard about it through a neighbor of the owner. The wife of the original owner said the turbochargers did not work, and she took it to the local Mazda dealer and they quoted her $4,000 to replace them.
The car fired right up when we went to look at it, but after running a little while the idle would bounce. I could tell that there had been some rodent activity in the engine bay and was thinking maybe a vacuum hose got chewed on, etc. A test drive showed that if you accelerated somewhat hard, the car would hit a wall at about 4500rpm and simply not want to go higher. It did not appear to be making much (if any) boost.
Once home, I drained the old fuel, and put in fresh 93 with premix. I also installed a new fuel filter. My initial goal was to do the full silicone vacuum hose replacement. I started to tear into it and found an air filter that was chewed and probably about 50% gone. As I continued to remove parts, I continued to find issues. The ACV was completely (100%) packed with what I assume was the air filter material. I took the rack solenoid out and tested every solenoid and actuator on the car. I found one rack solenoid that was faulty (relief 1), but everything else tested fine. All of the original hoses were in great shape and were not brittle, but I installed new silicone hoses and viton check valves from Dale. I also replaced the y pipe couplers with Samco silicone hoses. I installed new plugs, new wires, and the updated ignition coil harness while everything was apart. As far as the UIM is concerned, I found that the air idle control valve had a few pieces of debris(little seeds?) preventing it from closing fully. The AWS was packed full of debris as well. I also found that the opening for the idle control screw was plugged up. I cleaned everything up really well and buttoned it back up with new gaskets, fresh oil, and new belts.
Once completed, I fired it up and it instantly started idling the same as before. A quick drive revealed that the car would rev freely to redline and appeared to be making boost. The car appears to drive fine, but still has an issue when at idle. The rpm’s will fluctuate constantly, sometimes as much as 1k rpm (1k to 2k).
Some other things I have checked…I have checked the TPS and it is perfectly in spec, the fax idle cam separates correctly. Everything throttle body related appears to be working correctly. I recently dug back into it to inspect the EGR which appears to be working correctly, and also to install a downpipe (thinking the precat may have been clogged), but everything looked fine. I have checked for codes and do not get any. I just took the car for a small drive today, and it drives really well if you are just cruising normal, but the rpm’s will constantly fluctuate at idle. If you turn the A/C on, the idle will stay steady at 1300. When I tried to adjust the idle with the idle control screw on the throttle body, it has no effect at all…you can turn it several turns, and it does nothing. I have also unplugged the o2 sensor at idle and that did not make any difference either ( but I’m not sure it really should at idle). At idle the vacuum fluctuates between 17 and 10 inhg as the idle bounces.
At this point, I am getting discouraged. There is something I am missing and I’m just not sure what it is…I’m not sure what my next step should be. Maybe test for vacuum leaks, and do a compression test. The motor seems healthy to me, but I am not a rotary expert by any means. I am very confident that if it has a vacuum leak, it is somewhere deeper than I have touched.
Any input would be greatly appreciated. I would love to get this car back on the road! Attached are a few pictures.
Thanks!
Thanks! Yes, the wax plunger appears to be working properly, it separates once the car is warm. I am leaning towards the o2 sensor at this point, because the other day I let the car idle for a while and then unplugged it and it made no difference. I think my next step is to take it on a short drive and then come back and unplug the o2 just to confirm...if I don't hear a difference, I will order a new one.
Does it still have the old non-metal lower intake gasket? If so, spray some carb cleaner around it while it's running and see if the idle drops. The non-metal gaskets crack and pull unmetered air in.
I had a similar problem with a bouncing idle and found it was my lower intake manifold gasket. The old one was paper and chunks were missing. Replaced with new metal gasket and everything was fine.
Check for other leaks as mentioned with carb cleaner. LIM gasket is something I wouldn't want to do again. Was a pain.
I'm not sure if it has the non-metal LIM gasket, but I'm guessing it probably does if that was what it originally had. I have not had it apart that far to tell. Where is the best place to spray to check for a leak at the LIM? From under the car or above?
It doesn't sound like a fun job. I imagine everything on top needs to come out too? UIM, solenoid rack, fueling, etc?
A little update...my mechanic friend brought over his smoke machine the other night to do some testing. I took the black elbow off coming from the intercooler to the throttle body elbow. I then blocked the elbow to the tb and injected the smoke into the line used by the brake booster. We did not find smoke coming out anywhere, however smoke eventually came out of the intercooler.(where the black elbow would have been) I'm confused how the smoke which was being injected into the upper intake manifold got back into the intake side piping and started coming out the intercooler? This may be a novice question, or may be a hint to my problem?
My friend that came over is not familiar with rotary motors, but did say it does not seem like a vacuum leak to him. He was concerned that the base idle screw had no effect on the idle at all...whether it is fully closed or 5 turns out.
I did notice that if I unplug the air pump when the car is cold, the idle surging seems to stop. Once the car warms up it will then start bouncing again...this was the same thing that happened when I initially went to look at the car. I didn't realize it at the time, but the air pump was unplugged when we got the car.
I plan to do some more troubleshooting tomorrow with a fellow FD owner and will post our findings. If anyone has any input or can answer my question above that would be greatly appreciated!
I believe the air pump works with the ACV. I think it strategically injects air for reasons (sorry it's been awhile since I dug into that info and I'm being super vague). You can try unplugging the IACV and see if it idles differently. Otherwise it might not be a bad idea to look into whether the air pump/ACV system is working correctly.
Did you reinstall the Idle Speed Control (ISC) solenoid after removing? It's bolted to the UIM near the firewall next to the throttle body.
I left mine unplugged once after doing some work on the throttle body and it threw my idle all over the place. If yours was all clogged up it might be damaged.
How far in did you thread the idle speed set screw? You mention it was plugged and you had to clean it out. You might need to fiddle with that. This adjusts a bypass passage in the throttle body to allow more or less air into the manifold during idle. You will always have some air running past the throttle body to keep the engine running, it never fully closes. That's why you saw the smoke run back out towards the intercooler.
Yes, the ISC has been re-installed and hooked up. I misspoke earlier when I said the car does not idle any differently with the iacv unplugged...I should have said it does not idle any differently with the ISC unplugged. I have not unplugged the IACV and ran it(not sure you can access the plugs very easily with the UIM still on.)
As far as the smoke test, I removed the elbow between the intercooler and throttle body pipe. I then plugged the pipe going to the throttle body. Smoke eventually came out of the intercooler, so it had to get back into the system somehow, but I don't know how.
One thing I noticed is that if I unplug the air pump when I turn the car on, the idle does not bounce, but once the car is warm, it will start bouncing again.
A local FD owner came over the other night to do some troubleshooting with me and we took it for a drive. He was very impressed with how well it ran and said it was strong for a stock car. This was good to hear as his FD has 18k original miles and runs very well. He also owns an FB and he said that did the same idle bounce when he purchased it late last year. He said it went away on it's own after he put about 3 tanks of gas through it. Maybe I will be as lucky!
It looks like the mouse set up home in your intake. Did you thoroughly go through anywhere and everywhere it could have gone to include all the hoses? If it ran with that crap in there, it could have gotten sucked through your turbos and lodged in the IC. You may want to take that out and see if there's any debris at the bottom inlet.
I had the same issue for 2 weeks after going for an engine wash.
Went through the normal troubleshoot and still surged.
Lost count of how many times i adjusted the idle screw, culprit was the tps connector, unplug it found the pins on the connector and plug dirty. Sprayed some Q20 used a thin paint brush and cleaned it up. Plugged it back and surging gone. If all else fails, you can try that
Thanks, I will take a look at the TPS connector. It seems that the front upper idle screw might have previously been adjusted by the dealer in an attempt to lower the idle. The adjustment screw is not touching the stop on this car...you could probably slide a piece of paper between it and the stop. Talking with a fellow FD owner, he said that his screw is adjusted into the stop quite a bit. If it is adjusted into the stop the idle would raise however. I still think it is a solenoid or valve that is sticking or has debris in it. Occasionally it will make an annoying rattling noise which seems to be coming from the TB area, or behind the IM.
I had the same problem, idle woes, ~1100 to 1200 rpm surging. Also, coincidently, my car was parked for 11 years. I just started resurrecting it. I also had no apparent vacuum leaks.
Just found and corrected the problem(s) today.
First kads (post #17) describes contact issues on the tps connector. I had bled the coolant by removing the intake coolant hose. i think coolant might have gotten on the contacts or in the connector. I sprayed the tps connecter with crc electrical contact cleaner and reconnected. This helped, but the idle speed was still a little high.
Next I discovered that if I pulled up on the throttle pedal, then the idle dropped to 800 rpm. Drenched the throttle body and pedal mechanisms with wd40. Also shot wd40 into both ends of the cable and worked the cable back-and-forth to free it. Probably some dirt or corrosion inside the cable after the long storage caused it to hang up slightly.
Reporting back with some good news. A few weekends ago I made some very minor adjustments to the upper idle screw and the issue instantly went away. I have since put about 400 miles on it including a trip to Watkins Glen this past weekend for their vintage festival and the car performed flawlessly and idles at ~850. The next step is to install a Pettit AST and put the FC thermoswitch in.
07-19-15, 02:55 PM
Idle Woes
There is something I am missing and I’m just not sure what it is…I’m not sure what my next step should be. Maybe test for vacuum leaks, and do a compression test. The motor seems healthy to me, but I am not a rotary expert by any means. I am very confident that if it has a vacuum leak, it is somewhere deeper than I have touched.
