Removed and Reinstalled UIM, now hard to start/idle.
Two nights ago I removed my UIM to replace the Throttlebody Coolant Hose that goes from the Rear Iron to the Throttlebody as well as the coolant hose underneath the throttlebody.
After a relatively easy swap, I checked to make sure everything was secure and proceeded to reinstall the UIM. After I thought I was finished, I started the car and it ran like ass. The idle was unstable, showed low vacuum, and didn't rev properly. Assuming I messed up somewhere, I removed the UIM a second time to check for Vacuum leaks and what not. After replacing a few questionable hoses, I reinstalled the manifold again and started the car. Again it was hard to start, idled even worse, and pulled the same amount of vacuum (25mmHg according to PFC) The throttle needs to be depressed for the car to come on, it will sometimes idle by itself, but not for long. I put my hand infront of the TB elbow (intercooler not connected) and it does pull vacuum but it just doesn't sound good. Motor shakes and vibrates when you rev it. I have spent two days troubleshooting and searching the forums for keywords such as vacuum leak, leaks, vacuum, idle, starting, UIM, throttlebody and I am still stumped. I have checked every vacuum hose in plain sight (yes the MAP hose is connected). All bad or even marginally questionable hoses have been replaced with Baker Precision Silicone hose. The car ran flawlessly before I took the UIM off, I just wanted to replace the throttlebody coolant line because it looked sketchy and I figured it would be a safe thing to do... =/ Mods (though I dont think it should matter): 1993 FD3S Base APEXi PFC BNR Stage 3 Twin Turbo - Sequential GReddy Profec Type S M2 Med Intercooler GReddy Throttlebody Elbow RB Catback I usually don't resort to starting my own thread, but I am stumped. Can someone help me out? Possible connectors I forgot to hook up, sensors to test, hoses I forgot to connect? btw, all sensors check out properly on the PFC commander, nothing is out of spec. Spark plugs shouldn't be fouled, they were replaced about 500 miles ago. Fuel Filter replaced 300 miles ago. My references for this whole project: http://www.rx7.org/Robinette/manifold.htm http://www.rx7.org/Robinette/hoses.htm |
map sensor hose not connected?
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Originally Posted by CYM TKT
(Post 10661385)
map sensor hose not connected?
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Originally Posted by championadrien
(Post 10661378)
I have checked every vacuum hose in plain sight (yes the MAP hose is connected).
I didnt see anything about the gasket between LIM and UIM if its a paper one it could have torn without you noticing. |
It is possible that you knocked the tps out of adjustment. I would test/adjust it and see what happens.
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UIM/LIM Gasket is metal and in good condition.
Yes, MAP hose is connected. Thanks but still need help. =/ |
Recheck your work. Re-do all the steps you did and inspect. Most likely, if you remove the UIM and re-install it; whatever you missed last time you'll connect up the second time. We can't tell you what you missed or messed up since we don't know exactly what you did. If it worked before, then it's something you did so retrace your work.
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Make sure ISC is connected, I forgot that once and it idled rough.
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Originally Posted by Mahjik
(Post 10661588)
Recheck your work. Re-do all the steps you did and inspect. Most likely, if you remove the UIM and re-install it; whatever you missed last time you'll connect up the second time. We can't tell you what you missed or messed up since we don't know exactly what you did. If it worked before, then it's something you did so retrace your work.
Originally Posted by doofy
(Post 10661614)
Make sure ISC is connected, I forgot that once and it idled rough.
I'm going to try testing the TPS according to the FSM. |
You replaced the coolant line to the rear iron? Did you check to see if you knocked off anything for the fuel pressure regulator? You just really need to start shining lights in there and making sure everything that should be connected, is...
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25mmHg |
Originally Posted by Mahjik
(Post 10661824)
You replaced the coolant line to the rear iron? Did you check to see if you knocked off anything for the fuel pressure regulator? You just really need to start shining lights in there and making sure everything that should be connected, is...
Originally Posted by arghx
(Post 10661932)
25? you sure it's not at least 250?
Keep in mind the car does not idle stable, it surges randomly and the vacuum readings on the autometer gauge surge with it. The PFC vacuum/boost readings however stay at a constant 20 - 30 mmHg, with or without throttle. I've been staring at this mofo for a couple of hours and I can't find anything wrong with the UIM/TB/ or rats nest. everything looks solid. Could a hairline crack in one of the rats nest vacuum hoses even cause this much disturbance in the idle? I feel like I need to have a massive vacuum leak for the car to idle this bad. stumped....:scratch: |
rig up a pressure tester with PVC and a pneumatic fitting. Fighter's garage used to sell one. basically you plug one turbo inlet and then pressurize the other. Look at the example here for a 300zx Twin Turbo: www.boostpro.net/prodtester.html
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Sounds like a vacuum leak.
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If you reverse the gasket between the TB and UIM you will have a vacuum leak! the notch on top of the gasket must be on the firewall side. Good luck
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Originally Posted by arghx
(Post 10661976)
rig up a pressure tester with PVC and a pneumatic fitting. Fighter's garage used to sell one. basically you plug one turbo inlet and then pressurize the other. Look at the example here for a 300zx Twin Turbo: www.boostpro.net/prodtester.html
Do the rotor chambers even hold pressure with motor not in use? And what kind of pump should I be using to pressurize the chamber? I am currently using a standard hand pump connected by silicone.
Originally Posted by Erix7rew
(Post 10662357)
If you reverse the gasket between the TB and UIM you will have a vacuum leak! the notch on top of the gasket must be on the firewall side. Good luck
--- I replaced 1 more vacuum hose since my last post, its not that it needed replacing, its just because I could pull it off, so I figure might as well switch it to vacuum. I'm going to reattach everything and try it again. I feel like the problem is electrical but all the PFC sensors read within range and I just tested the ISC according to the FSM and it is in spec. Also I forgot to mention that while doing the coolant hose, I decided it would be a good time to replace the FD Fan thermoswitch with the FC one, however I still doing think that should make a difference since the thermoswitch should only affect when the fans come on and not what the ECU sees to adjust AFRs. |
Well I got a little bit of progress today. The idle can now support itself as long as I don't rev the motor, and I am pulling 250~290 mmHg. I'm not sure what it was because I took lots of things apart and put it back together. However it still runs like crap, backfires at the throttle let off, and if I let off the throttle too aggressively, the engine will kill itself.
Here is a video of the idle and what not - http://www.youtube.com/watch?v=s6g2A3Gb4XQ Idle - 620 RPM Vacuum - ~280mmHg on PFC/ 9inHg on Boost Gauge Inj Duty Cycle @ idle - 5.7% (2% higher than normal) AFR - ~16.7 (innovate WB, as engine rpm increases to 3000, AFRs go up to 19, I am running Stock Air Pump and Cat) I have the Idle Air Screw at half turn from all the way in, while the car was running I did try to adjust it but it looks as if it made no difference in the way the car ran at all. I'm gonna have the manifold off one more time and take a real good look at everything, but I seriously can't figure out what it is. |
Have you made sure the check valve that goes to the MAP sensor is installed correctly?
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Originally Posted by hondasr4kids
(Post 10663238)
Have you made sure the check valve that goes to the MAP sensor is installed correctly?
Dale |
Originally Posted by hondasr4kids
(Post 10663238)
Have you made sure the check valve that goes to the MAP sensor is installed correctly?
Originally Posted by DaleClark
(Post 10663262)
IT'S NOT A CHECK VALVE, it's a filter. People keep thinking it's a check valve.
Dale Thanks for everyone's input, but keep them coming. Car is still broke :( |
Just to explain... difficult to see but the gasket is embossed on one side only
http://i39.photobucket.com/albums/e1...3A1-13-655.jpg http://i39.photobucket.com/albums/e1..._1916661_n.jpg Good luck! |
Originally Posted by Erix7rew
(Post 10663360)
Just to explain... difficult to see but the gasket is embossed on one side only
http://i39.photobucket.com/albums/e1...3A1-13-655.jpg http://i39.photobucket.com/albums/e1..._1916661_n.jpg Good luck! |
Don't feel bad. Taking my UIM off before I've broken the tb to elbow oring, had check valves disintigrate in my hands, broken solenoid nipples, etc etc. It's always an adventure. Removing the UIM the last time led to a complete vac hose replacement, but it was time for that anyway. Shortly after that it cold start munched an apex seal leading to engine replacement. On the plus side it led me down the "replace all the old crap" path and now it's running great *knock on a pile of wood*
Did you check your harness for any plugs that might have backed out of the connectors, I've had that happen too. |
Originally Posted by scotty305
(Post 10663409)
Thanks for sharing, I had never noticed this before. I suppose there is a 50/50 chance I reinstalled this correctly the last time it was removed from the car.
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I had a somewhat similar issue the last time I removed the UIM. My idle was hunting all the way to about 3k rpms and would not hold steady. Adjusting the idle screw changed nothing. I had ended up changing the pre tension on the throttle cable when I removed it. So I ended up tweaking the tension on the throttle cable to get it almost perfect and using the idle screw to fine tune it.
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Originally Posted by RXtacy
(Post 10663851)
I had a somewhat similar issue the last time I removed the UIM. My idle was hunting all the way to about 3k rpms and would not hold steady. Adjusting the idle screw changed nothing. I had ended up changing the pre tension on the throttle cable when I removed it. So I ended up tweaking the tension on the throttle cable to get it almost perfect and using the idle screw to fine tune it.
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Originally Posted by 1QWIK7
(Post 10663715)
You didnt install this incorrectly. The distance from the bolts from left to right are different from the top 2 and the bottom 2. The gasket wouldnt even go on the 4 bolts if you had put the gasket upside down.
Originally Posted by RXtacy
(Post 10663851)
I had a somewhat similar issue the last time I removed
the UIM. My idle was hunting all the way to about 3k rpms and would not hold steady. Adjusting the idle screw changed nothing. I had ended up changing the pre tension on the throttle cable when I removed it. So I ended up tweaking the tension on the throttle cable to get it almost perfect and using the idle screw to fine tune it. |
Originally Posted by championadrien
(Post 10664240)
I wish that was my problem but the slack in my throttle cable is spec'd to the FSM. From what I understand it shouldn't be pre-tensioned, but there should be 1 - 3mm of play in the cable. Also, my vacuum readings are seriously low so I'm thinking mine has to do with an actual vacuum leak.
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championadrien
I had a similar problem just recently, where it had issues holding idle, backfiring and all that. Problem was definitely caused by an intake leak, I had took a can of carbcleaner and sprayed everything I could from the tb elbow back. Turned out the gasket for the ISC valve was bad causing the intake leak. I doubt you are having the same exact leak, but from you statements previously posted, sounds like some kind of intake leak. |
Originally Posted by RXtacy
(Post 10664247)
Have you sprayed carb cleaner around to check for vacuum leaks?
Originally Posted by phrost
(Post 10664259)
championadrien
I had a similar problem just recently, where it had issues holding idle, backfiring and all that. Problem was definitely caused by an intake leak, I had took a can of carbcleaner and sprayed everything I could from the tb elbow back. Turned out the gasket for the ISC valve was bad causing the intake leak. I doubt you are having the same exact leak, but from you statements previously posted, sounds like some kind of intake leak. -- After running a starter fluid and pressure test, if I can't get any solid results, I'm going to start taking the ACV off and looking under there for vacuum leaks, since the main rats nest seems to be solid. |
Originally Posted by RXtacy
(Post 10663851)
I had a somewhat similar issue the last time I removed the UIM. My idle was hunting all the way to about 3k rpms and would not hold steady. Adjusting the idle screw changed nothing. I had ended up changing the pre tension on the throttle cable when I removed it. So I ended up tweaking the tension on the throttle cable to get it almost perfect and using the idle screw to fine tune it.
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So...
Today I took off the ACV, replaced two hoses that looked iffy (but they had no cracks or anything) and started reinstalling everything. After I got the manifold on I started the car and no surprise, it still runs like buttocks. So I mess with the idle air screw and still nothing happens. After letting it run like crap for about 2 minutes I turn the car off and go look up some TPS related threads. I see that even though the TPS is within spec for the PFC, it wasn't TOTALLY within spec with this thread http://www.fd3s.net/tps_adjustment.html It was something like .12 off for the narrow range fully closed (1.37V). So I adjust it so that it is more within spec, however my TPS is probably not in tip top shape because once I get the fully closed within spec, the wideband Fully Open would be .09 under spec (4.11V). I guessed ah what the hell, I don't care about the fully opened throttle position, I just want it to idle, so I start the car again. No surprise, it runs like crap yet again. As I was about to give up, I decided to record a video so that I could post it on here and get more feedback, but while recording the video/blipping the throttle, I noticed my vacuum started to rise until it finally got to about 407 mmHg, or 13 inHg. After that I ended the video, and messed with the idle air screw and I was able to get it to idle perfectly at 720 rpm with 440 mmHg/16inHg of vacuum. So I have no idea what it was, but appearantly it was fixed, and it just needed a little bit of throttle action to bring up the idle/compression. After a short test drive, I noticed my car was pouring out blueish smoke, so I shut it off, and check some threads on oil smoke. Find that the PCV Valve can cause smoke and isn't necessary, so I go back to the car, eliminate it, and drive the car around and lo and behold, perfect idle with no smoke. So alas, the car is fixed. I have no clue what the problem was, but it was magically solved. Thanks everyone for your suggestions and hopefully this thread helps people with their vacuum leaks. Here's the said video of the magical recover: http://www.youtube.com/watch?v=afeQx8jrZhg |
The problem was your PCV valve stuck open! It act like a big leak if it's stuck open!
I'm glad to see that you solve this issue. |
Originally Posted by Erix7rew
(Post 10666611)
The problem was your PCV valve stuck open! It act like a big leak if it's stuck open!
I'm glad to see that you solve this issue. but at least its finally working. =D |
Idle speed control valve needs to get cleaned or you need to buy a new one. i had this problem before and that was it. also check your VTA1 and VTA2 readings on your power fc, it might be out of adjustment. if the idle is jumping around and it stalls or dies, its the ISCV and these suckers cost a lot of mone. As long as you dont have a vacuum leak this is one of the biggest and overlooked causes of bad starts, idles, and stalls...
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