hard starting and sluggish acceleration when engine is at operating temperature

[French02chris]

Ok...here is the story :

-cold start : engine starts right away ( less than 1.5 seconds ) and drives great!!!

when I drive to the supermarket ( or anywhere) and engine reaches temperature, the car will have a hard start ( 2.5 seconds) and acceleration will be a little slugglish until 40 mph.....then it will drive fine.

Car runs great on highway.....only issue would be when I stop for gas : hard start again and a little sluggish.

Test that I did : after hard start and stopping at a stop sign ( or traffic light ) , I would hold the brake pedal with left foot and give a little gas with the right foot (1000 rpm or so) : Car won't get sluggish.

idle is fine in neutral and in drive ( same as before the issue)

I tested fuel pressure at idle : awesome and within specs!! FPR as well.
switched throttle body : NO change ( selling the one that i remove, btw)
NEW fuel filter : NO change
NEW FPR : NO change
check the engine temperature sensor : seems to be in specs as well ( 323 and 326 when engine is under 80 degrees....can't remember values when engine was around 90 , but they were in specs too)
Cleaned spark plugs : NO change ( definitely NO gas on them)
newish caps , rotors, ignition coils and thingy behind the rotors are fine ( dry as it can be )
spark plugs wire are also newish.
NO smell of fuel in the car or under the hood
Fuel injectors seems to click the same ( used the screwdriver method)
NO misfire, NO rough idle...
put a bottle of redline SL 1 : NO difference
wiring harness in NOT the shitty ones

If i unplugged the MAF, there will be a little drop of RPM just when i unplug, but the car will compensate and idle fine again......

NO vacuum leaks

Car runs great on hwy with great acceleration ....kickdown works great too...

MPG is good ( 25 mpg yesterday on hwy for a full tank at 70-72 mph....with ac on most of the time)

Basically, I don't understand the issue!!!!

Any ideas???????

Would a bad check valve on one of the pumps cause hard starting when engine is warm???

 

[a777fan]

Did you test the fuel pressure ‘leak down’? IE - attach a fuel pressure gauge, key on engine off to get the fuel pumps to pressurize, then wait 30 min to an hour and recheck the pressure.

There’s a spec in the FSM for the residual fuel pressure after a certain time period. Something out of spec could be the result of a bad check valve; OR - what I would suspect in this case based on symptoms- a leaky injector.

 

[gsxr]

Would a bad check valve on one of the pumps cause hard starting when engine is warm???

Possibly - but I'm really not sure. Need to check fuel pressure at the engine when the hard starting is occurring.

 

[gsxr]

After the sluggishness and you get it above 40mph, does it have full power at full throttle to the redline? If so, it isn't likely to be fuel pumps (but you didn't mention pump replacement, and if original, they are due at 30 years old).

A very very long shot could be a failing crank sensor, which can sometimes cause really bizarre issues. No test other than replacing it and seeing if there's any difference.

Next is clearing all codes and seeing if any codes appear after the next slug-fest.

 

[French02chris]

Possibly - but I'm really not sure. Need to check fuel pressure at the engine when the hard starting is occurring.

Pressure is fine at idle... And hold for a good 3 hours
I made a post under 400e/e420...Hopefully you can find it.. Lol

 

[gsxr]

Pressure is fine at idle... And hold for a good 3 hours
I made a post under 400e/e420...Hopefully you can find it.. Lol

Did you specifically check rail pressure while it was cranking, and would not start? Normal pressure (50-55psi) but it just cranks and cranks? That's pointing back to possibly CKP as I noted in the other thread.

 

[French02chris]

Did you specifically check rail pressure while it was cranking, and would not start? Normal pressure (50-55psi) but it just cranks and cranks? That's pointing back to possibly CKP as I noted in the other thread.

I take 2.5 seconds to crank.. Then it is a little sluggish until I reach 40 mph... Only on hot start.
Cold start is great and runs beautiful on hwy... Did 1440 miles thru & Friday..
Idle is perfectly steady, engine temperature is good, and no misfire..
The sluggishness is only after I restart the car

 

[French02chris]

Did you test the fuel pressure ‘leak down’? IE - attach a fuel pressure gauge, key on engine off to get the fuel pumps to pressurize, then wait 30 min to an hour and recheck the pressure.

There’s a spec in the FSM for the residual fuel pressure after a certain time period. Something out of spec could be the result of a bad check valve; OR - what I would suspect in this case based on symptoms- a leaky injector.

pressure is still the same all the time.....about 48-50...after 30 minutes , i probably lost a couple of psi....
it took over 3 hours to get to 0 ( only because i had to drive somewhere, so i depressurized it)

 

[French02chris]

After the sluggishness and you get it above 40mph, does it have full power at full throttle to the redline? If so, it isn't likely to be fuel pumps (but you didn't mention pump replacement, and if original, they are due at 30 years old).

A very very long shot could be a failing crank sensor, which can sometimes cause really bizarre issues. No test other than replacing it and seeing if there's any difference.

Next is clearing all codes and seeing if any codes appear after the next slug-fest.

yes, I get full throttle to redline without any bogging!!!
Fuels pumps have 60K miles on them....

Also, I don't have any codes ( except for my SRS code which i had for about 5 years...lol)

 

[French02chris]

After the sluggishness and you get it above 40mph, does it have full power at full throttle to the redline? If so, it isn't likely to be fuel pumps (but you didn't mention pump replacement, and if original, they are due at 30 years old).

A very very long shot could be a failing crank sensor, which can sometimes cause really bizarre issues. No test other than replacing it and seeing if there's any difference.

Next is clearing all codes and seeing if any codes appear after the next slug-fest.

Also, yesterday as a test...I drove about 40 miles in backroads with AC on ( so, stop signs, traffic lights and a little of traffic in one of the towns in Maine) WITHOUT the fuel tank cap , and the car was way less sluggish ( almost back to normal....even with the long cranking time when hot)

 

[French02chris]

Did you test the fuel pressure ‘leak down’? IE - attach a fuel pressure gauge, key on engine off to get the fuel pumps to pressurize, then wait 30 min to an hour and recheck the pressure.

There’s a spec in the FSM for the residual fuel pressure after a certain time period. Something out of spec could be the result of a bad check valve; OR - what I would suspect in this case based on symptoms- a leaky injector.

as for leaky injector : I don't have any smell of gas around the injectors and they all are clicking fine.
Also, I check my oil every day and the level is the always same and the oil is not thinning . wouldn't a leaky injector leak fuel into the oil and thin the oil as well as increasing the level reading on the dipstick ??

 

[nocfn]

Interesting on the tank cap removal. I do not think this is your issue but has that furl fuel tank valve been changed yet - from tank to charcoal cannister?

 

[gsxr]

The change with tank cap removal was likely a coincidence... don't read too much into that. Also don't worry about gas entering the sump. Charcoal canister system wouldn't cause this either. Something else is going on here.

 

[French02chris]

Interesting on the tank cap removal. I do not think this is your issue but has that furl tank valve been changed yet - from tank to charcoal cannister?

no..it hasn't been changed

 

[French02chris]

The change with tank cap removal was likely a coincidence... don't read too much into that. Also don't worry about gas entering the sump. Charcoal canister system wouldn't cause this either. Something else is going on here.

i ordered a long fuel pressure line gauge ( arriving on Tuesday)...so I can drive around and checking fuel pressure at the same time....
IF the pressure change while i am driving, could it be my issues ( either fuel pump or fuel pump check valve)

Also as a precaution, I did order a NEW crankshaft position sensor

 

[a777fan]

as for leaky injector : I don't have any smell of gas around the injectors and they all are clicking fine.
Also, I check my oil every day and the level is the always same and the oil is not thinning . wouldn't a leaky injector leak fuel into the oil and thin the oil as well as increasing the level reading on the dipstick ??

I don’t think it actually takes much of a leaky injector to cause hard starting issues. A couple of drips into a cylinder may be enough to disrupt the AF ratios during start. Until you get a couple of cranks through to clear out the extra gas. Hence the longer start times.

The fuel rail on the M119 is accessible enough, you might think about popping the entire rail and injectors out of the head and just doing a visual ‘leakdown’ inspection just to make sure you don’t have a leaky pintle on one of em. Just cause an injector is clicking when power is applied doesn’t mean the pintle seals properly when closed. Short of your time, this step wouldn’t cost you anything either.

 

[French02chris]

I don’t think it actually takes much of a leaky injector to cause hard starting issues. A couple of drips into a cylinder may be enough to disrupt the AF ratios during start. Until you get a couple of cranks through to clear out the extra gas. Hence the longer start times.

The fuel rail on the M119 is accessible enough, you might think about popping the entire rail and injectors out of the head and just doing a visual ‘leakdown’ inspection just to make sure you don’t have a leaky pintle on one of em. Just cause an injector is clicking when power is applied doesn’t mean the pintle seals properly when closed. Short of your time, this step wouldn’t cost you anything either.

sorry about all the questions....
would a fuel injector only leak when engine is at temperature??
if/when i do a short drive to the store (not even a mile), and the engine hasn't reach operating temperature, then the car starts fine (1.2 second crank)

 

[Jlaa]

Just for kicks, do you have pictures of the current upper wiring harness? I know you said "wiring harness in NOT the shitty ones" but maybe its good just to triple check the ZD/FD dates .... of course the upper wiring harness drives the injectors and heat soak can cause a disintegrated harness to do weird stuff……

 

[French02chris]

The change with tank cap removal was likely a coincidence... don't read too much into that. Also don't worry about gas entering the sump. Charcoal canister system wouldn't cause this either. Something else is going on here.

BIG UPDATE :

I finally found my code reader and re-read the codes !!!
PIN 4 : code 8
PIN 7 : code 6
PIN 8 : Code 5 and 6
PIN 17 : Code 6

 

[gsxr]

Great! Now clear all those, drive the car, and see which ones return.

 

[JC220]

Why are there 2 threads on this car running at the same time(?)

Would it be an idea for moderators to merge these threads?

 

[JC220]

I see more here on this thread about the fuel pressure being tested.

Just note that a bad pump check valve can be intermittent and hard to detect....

 

[gsxr]

I was thinking the same thing, Joe, but he said the fuel pumps have 60kmi on them. I'd be surprised if one was failing already. Still, it would be nice to view "live" pressure when the sluggishness occurs.

 

[French02chris]

Just for kicks, do you have pictures of the current upper wiring harness? I know you said "wiring harness in NOT the shitty ones" but maybe its good just to triple check the ZD/FD dates .... of course the upper wiring harness drives the injectors and heat soak can cause a disintegrated harness to do weird stuff……

date built is around 2004, 2006 or 2009...I can't remember now, as I am away from the car..

 

[a777fan]

sorry about all the questions....
would a fuel injector only leak when engine is at temperature??
if/when i do a short drive to the store (not even a mile), and the engine hasn't reach operating temperature, then the car starts fine (1.2 second crank)

Scenario: perhaps the leaking injector only does so for a short time after engine shutdown while the fuel rail is still fully pressurized? If you leave and return to the car within a short amount of time, the leaked fuel would still be in the impacted cylinder and disrupt the start sequence. If left for a longer amount of time, the leaking injector eventually stops as the fuel rail pressure decays, and the fuel that does leak into the cylinder has time to evaporate.

Just a theory!

 

[French02chris]

FINAL UPDATE (hopefully) about my hard starting when warm/hot ( basically with engine above 80 degrees)

Received my camshaft position sensor....installed it, cleared the codes and went for a couple of drives ( with AC on, a few WOT acceleration, and a few stops where i would turn off and restart the engine)....also went to the gas station to put more gas.

Car restarted fine ALL THE TIME!!!!
also code didn't come back for camshaft sensor...
I think ( and hope) that my hard start issue is fixed!!!!! ( less than 1.4 seconds to restart the car all the time)

 

[gsxr]

That is great news!

Just to confirm, was this the camsmaft sensor at the top of the engine (front of driver cylinder head), or the crankshaft/flywheel sensor located at the back of the engine?

 

[French02chris]

That is great news!

Just to confirm, was this the camsmaft sensor at the top of the engine (front of driver cylinder head), or the crankshaft/flywheel sensor located at the back of the engine?

the camshaft ( top of engine)....I had code on pin 4 and pin 17 for it

 

[Matin]

Can anyone provide the p/n for the camshaft sensor, out of curiousity?

 

[French02chris]

Can anyone provide the p/n for the camshaft sensor, out of curiousity?

0021539528​

 

[gsxr]

The cam sensor is a very rare failure IME... but if you have a persistent code #8 on the LH module that returns every time after clearing, and the wiring/connection is good, then the sensor may be bad (as in this case). Only buy OE/Genuine though, the Facet/Hella sensors are Chinese garbage. I'd installed a used OE sensor before new aftermarket.

 

[dreaming.haze]

A follow up so not to create a new thread on similar things.

Seeing similar codes / results returned on a blink code read out. Found a spread of codes, Code #8 on LH / Code #5 & #6 on EZL / etc. Cleared things out for a drive and saw Code #5 / #6 on the EZL module return.

Focusing on the #6 code and the replacement of the CMP sensor - I decided to see what was in my car. Looks like I've got an FAE 79099 installed currently. With @gsxr 's note above, I was thinking of trying to find an OE replacement rather than try and chance it with a China made example. Going to try and swap the one currently installed on my 500E to see if the sensor swap will result in better performance + no codes.

If it is confirmed the sensor itself is the issue - does anyone have an OE replacement in their used parts stock that they'd be willing to part with? If not, I'll go with one off eBay.

 

[dreaming.haze]

Update after sensor swap - OE unit from my 500E worked a treat. Smoother running all around and better throttle response once things warm up a bit. Going to give it another days worth of driving and then see if there are codes displayed. Still other running issues to nail down, but progress is being made.