Whats up everyone,

Lately my car has been having a poor cold start issue that is driving me crazy. Whenever I start my car 1st time of the day it will start and the rpm will jump to about 1500 and then immediately acts like it hit a wall and drops down to about 700-900rpm. After about a minute or 2 the idle will begin to rise to about 1000-1100.

On a side note also related to cold starting is if I hit my gas pedal slightly before the car has fully warmed up the idle will drop slightly before rising. This goes away once the car has fully warmed. I believed this to be an out of spec TPS so I re-calibrated it per TSRM and it still does it. Then I tried 3 different TPS and still same issue.

To try and remedy these issues I have done the following.

• Replaced TPS
• Re-calibrated TPS
• Installed new coolant temp sensor
• cleaned IACV
• Tried a different ECU
• Checked coils
• Checked spark plugs
• Tried different ignitor
• Checked wiring
• Checked Timing
• Checked all sensor connections

When the car is warm it drives and idles fine.

My current mods are

• Walbro 450 fuel pump
• TT ECU
• TT MAP
• VVTI-Coils
• Boost cut controller
• BW S362sx-e
• Turbosmart Hypergate 45
• HKS racing BOV
• HKS IC
• AEM X-series AFR gauge
• AEM X-series boost controller
• Q45 Throttle Body
• 440cc injectors
• rebuilt motor
• FFIM
• No A/C

Any suggestions are appreciated.

Thanks

 

Take the BCC out of it and see if anything changes. it affects the map signal. When did the issue start what was the last thing u did b4 it started? Could be the Ecu, i've been thinking of sending my TT ecu in before it starts causing problems

 

Hmmmm honestly cant remember what the last thing I did was before I started experiencing this issue. I believe the last thing I did was replace the distributor as mine was leaking oil from inside, not sure if that could be the problem or not.

I will try starting the car without the BCC and see what happens.

Also the 2 TT ecus I have have been rebuilt. 1 by me and the other by Driftmotion.

 

Took the BCC out and no change.

 

When you replaced the distributor did you recheck the timing, it almost always is in a different spot and should be rechecked you could be advanced and the ecu is freaking out.
Otherwise that really really sounds like an improper tps position at idle. how did you re-calibrate? I see you have the q45 throttle body, are you using an adapter or just wires the q45 tps to the tt ecu?
It is really difficult to get it set just right with the q45 throttle body and the adapter, so that may be part of the problem. using just the q45 tps itself I am not sure that even works well but some people do use it.

If you messed with your throttle stop screw, my suggestion would be to back it off a hair and see if the tps is any happier with the lower values, could be a quick fix without a whole adjustment procedure.
And check the timing of course, put the jumper in and listen for the sound or that is another sign of tps issue.

 

Whats up Ali SC3,

I was hoping you would chime in as I went TT ECU because of your thread haha.

I will check the timing again.

I am using the Toyota TPS with the Q45 adapter. I have messed with the throttle stop screw as a means of increasing my idle due to the clutch and afterward adjusted the TPS using .55 & .66 feeler gauges as I dont have the exact ones that the TSRM calls for. I made it so the .55 feeler gauge gives a resistance of .5K ohms or less and infinite with the .66 feeler gauge.

After I replaced the distributor I made sure to put the timing back at about 7-8 degrees with the jumper wire in. I re-checked the timing about a week ago and it was still spot on and once I removed the jumper I could see that the timing changed as it should.

I feel like I have put the TPS in every possible position at this point haha. Is there a better/easier way to try and get it in sync where it needs to be. I have even tried doing it by ear where you hear it click when its engaged and just back it off slightly.

 

Yeah the feeler gauges don't wont too well with the q45 throttle body (or in general I find), I always do it by feel where you back it off slightly cause the adapter makes it vague.
My guess is you are too close to the edge where idl turns on/off, and it happens here and there when cold especially.
Try rotating the tps to where it is less engaged, as in back it off slightly more.

Also did you shave the extra stuff off the side of the q45 throttle body? it has a mechanical built in idle up thing based on temperature, I want to say for cold starts.
If you do not disable this then depending on temperature the throttle will sit in slightly different positions at idle which means slightly different tps readings.
Overall the q45 is picky to get right with the stock tps, so I am pretty sure it has to do with the tps signal due to the throttle body adapter issues.

I would go ahead and also set the timing at 8 degrees. when you start getting too close to 6 it seems to not run as well/strong.

 

Ok, I will try turning the TPS back a little bit and adjust the timing more so to 8. I did remove all the extra un-needed throttle linkage and plunger thing on the front and shaved the arm off.

Thanks for your suggestions. I will report back shortly.

 

*Update*

I adjusted my TPS back a little bit and it seemed to help a little bit as the cold start idle went to about 1000 RPM. I did also adjust the timing a little more in the 8-9 range. I have not tried another cold start as of yet but I will report back later today.

1 more thing I forgot to mention that recently started happening is on occasion the needle on my tachometer wont move at initial start up. It will just sit at the bottom as if the car is off and then boom its up and running. Could this possibly have something to do with the distributor? The distributor was used so maybe it is having a signal issue.

Thanks

 

That's an interesting one, not so sure about the distributor being the issue on that one or you would pop up some codes or have misfires, I think that one has to do with the actual rpm board on the cluster or maybe something with the ignitor circuit isn't fully grounded.
Also make sure that grey noise filter remains plugged in, it is normally by the stock coil on the passenger side of the harness. Must stay plugged in or you get noise all over the ignition system which causes problems (not always but high rpm's or with lots of radio interference etc..).

 

*Update*

I have dialed back the TPS 2 times now from the engagement point and it seems to have helped out with the drop in idle when slightly touching the gas pedal. I have ensured the timing is dialed in at about 8-9 degrees and the car seems to be a little bit smoother.

However I am still having the original problem with the low cold start idle. First start of the day the car will start right up and the RPM jumps up to about 1500-2000 RPM and then immedietly drops down to about 1000-1050 RPM. After about a minute or 2 the O2 sensor has heated up and the AFR's begin to level out and the RPM begins to drop to its normal spot of about 750-800 RPM.

I just want a nice normal crispy cold start haha.

 

I still have the noise filter in place and I put in a different ignitor just to see if it helps at all.

Thanks

 

*Update*

New symptom the car is now having trouble starting all together. It will turn over perfectly fine and eventually putter to life after a few attempts.

When it does finally turn over the idle is worse than before instead of the rpm starting high it starts low and slowly builds its way up to about 800 RPM on a fully cold motor.

Any ideas?

 

Check fuel pressure and filter/ the check valve. I'm pretty sure my check valve is bad because if i key the car up and let the fuel pump turn on and flow the car always starts right up. but if i try to throw the key in and try to start it right away sometimes it sputters and slowly starts or dies

 

Ok, thanks for the suggestion. I did replace the fuel filter about 2 years ago. I do have a walbro 455 with the 12volt mod, so the pump does switch on with the key in the on position. Normally I will get in the car and put the key to the on position let the pump turn on and prime the system. This has not made a difference.

Is the check valve in the fuel filter? I think the fuel pump also has a check valve.

How do you go about checking the valve?

I will do a fuel pressure test. Should I perform this at startup or once the car is started and warm?

Thanks