Engine trouble - various issues

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ElmerFudd
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Engine trouble - various issues

#1

Post by ElmerFudd »

Hello guys and girls

The time has come to try and sort out some issues with my coupe, if you wouldn't mind helping me diagnose the causes as I'm far from an expert when it comes to engines but I do know my way around a tool kit.

I have a gen 3.5, 2.7 v6, 55plate.

I will include all problems in this thread just incase they are linked and possibly help with diagnosis. However if we concentrate on problems 1-3 first so we don't get confused with crossed information.

I apologize for the long post, just want to get as much information in as possible.

The problems.

1. Intermittent stall/drop in revs on start up. For instance I can jump in the car, start it up fine, runs fine, go to petrol station, get back in and bang, trouble starting. Sometimes it doesn't start and struggles, it turns over but takes time to fire, but always fires, it has never failed to fire up. Once it fires it can be fine and runs smooth, other times revs drop to about 500rpm and feels like it will stall, other times it will stall. So very inconsistent and erratic in behaviour. I do have a video of starting and revs dropping

https://youtu.be/4fLfWtdoa6I

2. When idle, revs drop for a second then back up. (This may have 5min intervals, 30 seconds, 2 min, 3min etc. It can happen a lot or not at all, very irregular on timing for this issue)(I do feel this is probably linked to problem 1)

3. When pulling away engine seems to shake/revs drop when I wouldn't expect it to, I've tried plenty of revs and still seems to be there. Again intermittent sometimes it happens other times it doesn't (Again I feel this maybe linked to problem 1+2)

4. When accelerating hard in 2nd and 3rd gear between 1000rpm and 3400rpm, the engine seems to pull back. So engine accelerates for 1 sec, pulls back 1 sec, accelerates 1 sec, pulls back 1 sec etc making the car kangaroo up the road until I reach 3400rpm, at which point the pull backs stop and car takes off as normal. Once the car has run for 5 mins or so this seems to ease off and eventually disappear. Also seems to happen more in the mornings so maybe the cold is affecting it. This problem is intermittent and doesn't always occur.

5. Car seems down on power between idle rpm and 3400 rpm. Mostly noticeable in 2nd and 3rd gear. It's not terribly slow, but at 3400 rpm it's like a turbo kicks in and bang the car seems to pull with a lot more grunt. This issue is there all the time and is the only issue that is not intermittent (Possibly related to issue 4)



Ok so those are the issues I face.

No engine light has ever come up to say there is an issue, but something is not right for sure.

What I have done so far.

New maf sensor (no change noticed)
Clean iacv and new gasket(I did have a problem with idle rpms jumping around quite a lot, found gasket cracked, this issue has gone now and rpm is consistent, except for the issues as above)
Throttle body cleaned (no change noticed)
New fuel filters(no change noticed, although things do seem smoother(placebo?probably))
Induction kit fitted as old intake pipe had a big crack (no change noticed regarding above issues, it did at the time make the engine feel better and run smoother but issues still persisted)
New brd poly rear engine mount(old was gone, thought this might relate to issue 3, however no change notice)

New spark plugs and HTC leads are on order however I don't feel this is going to make a difference as service manual say plugs were changed not so long a go.

Car has a full service history so oil and filters and such should have all been changed regularly.

Engine itself, to me, sounds fine, pulls well, no weird noises, sounds smooth. Slight tap noise from injectors but that is common as far as I know. Had a family friend who is a mechanic listen while he was at the house and he said engine sounds good. So as far as im concerned the engine is good and solid.

I don't feel the problems are mechanical as such. But more than likely a sensor or communication issue.

I'd prefer to fix this myself as I'm good mechanically, just engines aren't my usual subject matter. Plus garage prices can get ridiculous for time spent troubleshooting issues.

As i say I'm no expert so any help you guys can offer is much appreciated.

Thanks guys


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Re: Engine trouble - various issues

#2

Post by zen135 »

Sounds like clogged injectors. Try running a full bottle of a good PEA based cleaner such as Red Line SI-1 in a full tank to clean up the complete fuel system. Available at carparts4less and opie oils.
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Re: Engine trouble - various issues

#3

Post by paulchadwick »

I'm interested to see the responses on this as I too have the same idling issues.

I've already banged a full bottle of redex through and its made little or no difference.
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Re: Engine trouble - various issues

#4

Post by robbo »

have you tried cleaning or replacing the crank sensor?
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Re: Engine trouble - various issues

#5

Post by ElmerFudd »

Thanks for replies.

I have not tried the crankshaft sensor.

Sorry to say but I'm not familiar with the engine, where would it be. I assume near the mid to lower part of the engine near the crank obviously. But which side? Next to what?

I will pick up a bottle of injector cleaner when I'm next near somewhere that sells it
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Re: Engine trouble - various issues

#6

Post by dantanner »

As Robbo says CPS/TPS was often the cause of difficult starts after short journeys so def check those. As for the hesitant acceleration if the plugs/leads don't fix it it could potentially be coils (had this very issue on my Vauxhall Adam and it was a dodgy coil)
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Re: Engine trouble - various issues

#7

Post by Shel »

The Crank Position Sensor is down on the block behind the front header.
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Re: Engine trouble - various issues

#8

Post by ElmerFudd »

Shel wrote:The Crank Position Sensor is down on the block behind the front header.
Thanks, I did see this picture on Google, is this the same for the v6 also? Front or back? As v6 has 2 headers :handgestures-thumbupleft:
dantanner wrote:As Robbo says CPS/TPS was often the cause of difficult starts after short journeys so def check those. As for the hesitant acceleration if the plugs/leads don't fix it it could potentially be coils (had this very issue on my Vauxhall Adam and it was a dodgy coil)


Thanks, I will see how the new leads and plugs work, if not I'll have a look into the coils.
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Re: Engine trouble - various issues

#9

Post by Shel »

ElmerFudd wrote:
Shel wrote:The Crank Position Sensor is down on the block behind the front header.
Thanks, I did see this picture on Google, is this the same for the v6 also? Front or back? As v6 has 2 headers :handgestures-thumbupleft:
dantanner wrote:As Robbo says CPS/TPS was often the cause of difficult starts after short journeys so def check those. As for the hesitant acceleration if the plugs/leads don't fix it it could potentially be coils (had this very issue on my Vauxhall Adam and it was a dodgy coil)


Thanks, I will see how the new leads and plugs work, if not I'll have a look into the coils.
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Re: Engine trouble - various issues

#10

Post by ElmerFudd »

Shel wrote:
ElmerFudd wrote:
Shel wrote:The Crank Position Sensor is down on the block behind the front header.


Ah sorry, should read things a bit better in future :icon-lol:
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Re: Engine trouble - various issues

#11

Post by Shel »

ElmerFudd wrote:
Shel wrote:
ElmerFudd wrote:


Ah sorry, should read things a bit better in future :icon-lol:
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Re: Engine trouble - various issues

#12

Post by ElmerFudd »

Update!

So since posting I have installed the new HT magnecore leads with new bosch double iridium plugs.

I'm having trouble with crankshaft sensor though. Hyundai supplied me one costing £65 which I thought was alright until I fitted it and it didn't work. After investigation I found it was the wrong one for the car. They want approx £310 for the v6 crank sensor.....hmmmm a bit steep. So I tried a third party one and although it works, most of the issues In my op still remain and it also now stalls when idle on the odd occasion, which always throws a code relating to the crankshaft sensor so I need to find a decent replacement and hopefully that may sort problem 1.

I chucked in a bottle of injector cleaner

Car has also had a new fuel pump and filters but that's another story.

However for now problems 2 and 4 seem to have disappeared. What it was that fixed them I couldn't say as I've messed and tinkered with it during some problems that needed me to change the fuel pump along with the other stuff mentioned.

Things got worse for awhile but now seem to be narrowing down the list and getting better.

So any ideas where I can get a v6 crankshaft sensor would be welcome.

Thanks so far for the help
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Re: Engine trouble - various issues

#13

Post by nissan300zx »

engine temp sensor can cause the same issue, its telling the ecu its still cold when in fact its warm. giving it to much fuel hence the trouble starting when you have just done a short run, also the other symptoms can be caused by the same thing. its over fueling. with a go and its a cheap part to replace.
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