My Integra (2000 auto LS 180,000 miles) is acting funny. It runs and drives fine, but on cold starts, it idles really rough for the first 15 seconds or so, like it is only firing on three cylinders, then it cleans up and idles smooth. I have been cleaning and replacing parts/sensors one by one over the past several months and every time it seems to fix the issue only for it to come back after a few days. So far I have done the following:

Had the fuel injectors cleaned/balanced/rebuilt by precision auto injectors
Replaced the fuel filter
Replaced the cap/rotor/wires and plugs
Replaced the ECT sensor
Replaced the main relay
Replaced the radiator/hoses/thermostat
Cleaned the throttle body/ air idle control valve
Replaced the PCV
Cleaned the air filter
Replaced the cv joints/axles
Bled the brake lines and new brake pads
New battery
Some of that is irrelevant. I am just trying to name all I can, but I am sure I am forgetting some stuff.

Some things still on my list of to dos is:
Replace cam position sensor
Test/replace TPS and Map sensor
Replace o2 sensor(s)
Replace or clean the IACV again
Inspect/replace all vacuum lines, fuel lines and the Evap canister system
Check mechanical timing and ignition timing
Replace fuel regulator and fuel pump

It seems to only have this issue on cold starts, hot starts seem fine.
Also the car always seems to stink like fumes. I looked at the Catalytic converter a few months back and it looked clean/white, it didn't look clogged, so I am wondering it the EVAP system is clogged/leaking/faulty.

Thanks for any advice or tips.

 

Check the rubber gasket of the MAP sensor, maybe put a little silicon grease on it to get a better vacuum seal.

Also before you do another cold start just take the air cleaner off and see if there is any difference in how the motor starts. This should eliminate an air flow restriction causing a too rich mixture at start condition.

What was the color of the spark plugs you pulled out? Reading spark plugs can tell a lot. Light tan is a good color. Light gray is OK. Dark gray or black is too rich.

 

did you replace the ECT sensor or ECT switch? Sonds like the ECT sensor but maybe you replaced the switch not the sensor..

 

At the time I replaced the spark plugs, they looked to be on the lean side. So I changed the fuel filter and had the injectors serviced. I will double check them when I replace the FPR this weekend.

Thanks for the tip about the map sensor o-ring, I will do that too. The car has an AEM short ram that I have cleaned a few times, I don't think the filter is causing any restrictions, but I will give it a try.

 

The sensor is on the side of the cylinder head under the distributor and the switch is on the thermostat housing correct? I definitely replaced the sensor as they have totally different threads and won't interchange (trust me I tried on accident lol)

 

Having the same issue, post back when you find the solution.

 

Will do.

 

Then to me it sounds like the IACV is going bad and cant compensate enough air on cold starts until the the engine reaches op temp.

 

I took the IACV out and cleaned it a few months back. It seemed to be in good shape. My base idle is a little below 1000 and my cold idle is a little below 2000, so I think the IACV is working fine.


If i turn the key to the on position and wait a minute before starting, it seems to start fine. It is only when I put the key in and immediately try to start the car, that the rough cold start happens and even then,it only lasts for 10 seconds and clears up (well before the engine reaches operating temp). So if it is an IACV problem, it is just that it is not quite opening fast enough....?

That is why I am currently leaning toward the FPR. I am thinking that the FPR is faulty and my fuel pressure is not building up like it should when the fuel pump is priming. Also, the fuel pump used to only prime for 3 seconds and not it doesn't stop, it just keeps going.

 

I ran the codes yesterday. I expected the misfire codes, as it does run rough and misfire sometimes on the initial cold start, but the transmission code, I was not expecting that...

I need to pick up a timing light soon, but I just ordered an OBD2 scanner, so I will be able to double check the TPS/MAP/o2 etc... sensors soon, instead of just buying new ones and slapping them in.

 

So I am thinking now that I am going to order a new "Neutral Safety Switch", (The swtitch that bolts to the shift linkage. I don't think the 94-01 Integras had a "transmission range sensor" that bolts on to the side of the transmission).

00 2000 Acura Integra Neutral Safety Switch - Transmission - Genuine, Standard Motor Products - PartsGeek

Then I think I am going to clean out the transmission solenoid filters, replace the FPR and check out the outputs of the TPS and MAP sensor etc on the OBD2 diagnostics tool.

 

Just got done replacing the FPR. I can't say that it fixed cold start, since I haven't cold started it yet, but man does it run better. The low-end feels much better. There is no more lean surging and it can accelerate cleanly now where I would have needed a down shift to get going before.

 

Does fuel pump still prime for longer then 3sec.?

 

Oem fprs are pretty dependable. I'd the pump keeps priming I would think relay or ignition. Try to see if you have excessive play in the ignition. See if turning it back to run manually helps rather than just releasing the key.

 

Yes the fuel pump primes continuously. I am going to try the original main relay again and see if it is just the cheap autozone relay that doesn't have the three second timer in it or something. Or if it is the ECU or a fuel pressure sensor that cuts the fuel pump after 3 seconds of not starting the car with the key in the on position.

Also I pulled the plugs and left the pump priming for a while. the injectors do not appear to be leaking, as if that were the case I probably would have seen fuel running into the cylinders.

 

I am not following you on the "turning back to run manually".

Anyways, after replacing the FPR, the car runs a million times better, so I think that was a win, maybe not in the cold start issue, but in the overall driveability of the car, it is really really apparent.

 

I used to have a problem with my old car, where the key would not snap back to the run position, I would have to manually turn the key back to run from start. It's common for some newer honda ignition switches to go bad. If your check engine light doesn't turn off, it's the ecu. But the pump priming sounds like the relay or ignition.

 

So I got one of those bluetooth obd2 adapters and now I can get all of the live sensor data, like TPS, coolant temp, MAP, IAT, o2, fuel flow etc....

Funny thing is, closed throttle shows 9.8%, while open throttle shows 89%.
This sounds fishy to me, but forum research shows it to be spot on normal. I need to dig through the service manual, so I can see exactly what the resting and operating range and output of all these sensors is supposed to be.

With the engine off and key on, the MAP is showing 0.1 psi, which seems about right with me being at about sea level here. I am wondering exactly how much vacuum I should be pulling at idle.

Side note, the pre cat and post cat o2 sensor voltages seem pretty close, so I don't think the catalytic convert is doing much. I am wondering what those voltages should be at with the engine up to temp and idling. I really wish that I could find an AFR setting and an injector duty cycle reading as well.

 

It is the ECU that controls the priming, it should not prime constantly. 94

 

Interesting. I need to find my original main relay to double check that isnt related.

 

Okay I went through the TPS voltage last night.
5.02V input
0.52V Output at closed throttle
4.50V Output at Wide open throttle

That sounds about perfect to me.
Okay so the TPS has now been official ruled out. Time to move on to the MAP sensor. Does anyone know what those voltages should be at? Thanks guys.

 

Check the map sensor O ring. Also the ECT sensor its the bigger sensor next to vtec soliniod not the ECT switch on the thermo it could be bad causing rough idle on cold starts.

 

The ECT sensor in the head has been changed and it is brand new. I do need to look into the MAP sensor oring and the voltage in and out. I just need to find out the voltage specs from Honda.

 

Changed out my fuel pump for a High pressure Walbro 255 this weekend. I haven't had a hard start since, hopefully it stays this way. Driving around town, there seems to be a smidge more low end and less lean surging. The pump is a tad louder than stock, but no where near as loud as I thought it was going to be. It is audible when priming, but not really noticeable while idling. Most importantly, it was a direct drop in, no modifying needed, the hardest part of the install was removing and reinstalling the rear seat lol.

 

The car STILL has a hard start from time to time and has shown a cylinder 3 misfire a couple of times. I have since replaced the distributor, set the ignition base timing to 16 degrees (it was way off) and replaced the upstream o2 sensor. As usual, the car seems to run great after doing the mod, then eventually has a hard start/ rough running again. It doesn't do it every time, just every now and then, takes to long to fire and then runs on 3 cylinders for 10 seconds or so. I am unsure of the exact problem, but I am concerned that the head gasket may be slowly letting go and leaking in a tad of coolant into cylinder 3, after shut off and giving that cylinder a misfire/ or knock until it is burned off.