hesitation - fuel starvation??

[Dragan C]

Got a lack-of-power problem. I thought it was the distributor spring issue so I rebuilt that. Then I thought it was lack of back pressure due to my holey exhaust so I replaced that (catalytic looked good so I didn't replace that; no obvious cracks in downpipe). Each effort improved my throttle response but I'm still suffering from hesitation and/or sluggish acceleration. What should I try next? Maybe something simple like blow off valve or PCV? Or does this group think it's my fuel pump(s) or injectors?

Thanks!

Dragan.

[Bob Martin]

I'd look for a crack in the exhaust manifold. This can throw the O2 sensor off. Do you have a check engine light? If so, what is the code that has been thrown?

Bob

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[Dragan C]

Thanks for the feedback, gents. I should have mentioned I've already put on new cap, rotor, wires, plugs, and coil. No CEL. I'll try fuel filter next and then the pump; expect an update soon.

Dragan.

[Other]

I got your replies: thank you! I tried to keep the thread alive via my mobile but I couldn’t post - I could only reply. So, I went back to my desktop and was able to add to the thread. Btw, I started the new thread at my desktop through “+ New conversation”. 

Dragan. 

On Aug 6, 2021, at 12:48, nowi...@yahoo.com wrote:



Joel, I sent two replies that are not on the board.  I do believe Dragan received them though, through the email system only.

 

Also, note that this conversation shows up in a new topic?

 

Dragan, or Joel, how do you start a NEW TOPIC?   I see no opportunity to do so.

 

Thanks.

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/84a0c8fb-33fb-40c4-9536-a0bdc8eef70cn%40googlegroups.com.

[Dragan C]

For nowi...@yahoo.com the "+ New conversation" button is here:

[Joel Sass]

Hello! to start a new topic, I believe you just send an email to 323...@googlegroups.com. The subject of the email will become the topic.

On Fri, Aug 6, 2021 at 12:48 PM <nowi...@yahoo.com> wrote:

Joel, I sent two replies that are not on the board.  I do believe Dragan received them though, through the email system only.

 

Also, note that this conversation shows up in a new topic?

 

Dragan, or Joel, how do you start a NEW TOPIC?   I see no opportunity to do so.

 

Thanks.

 

From: 323...@googlegroups.com <323...@googlegroups.com> On Behalf Of Dragan C
Sent: Friday, August 6, 2021 11:56 AM
To: 323gtx <323...@googlegroups.com>
Subject: Re: 323GTX Group hesitation - fuel starvation??

 

Thanks for the feedback, gents. I should have mentioned I've already put on new cap, rotor, wires, plugs, and coil. No CEL. I'll try fuel filter next and then the pump; expect an update soon.

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/84a0c8fb-33fb-40c4-9536-a0bdc8eef70cn%40googlegroups.com.

[Dragan C]

Update:

- MAF good.

- fuel pump bad - replaced. Fuel sending unit replaced (gas gauge works again!).

- catalytic converter bad. The outlet looked good when I replaced the exhaust but the intake side is really clogged. I have a replacement.

- downpipe bad. There's a hairline crack in it. I have a replacement.

- intake piping and intercooler - all filled with oil! It appears that the oil temp sending unit was bad for a very long time..... All flushed and cleaned. I replaced the PCV and have a replacement sending unit.

So, through the process of elimination (distributor, exhaust, MAF, fuel, and now clogged cat) my SME (subject matter expert Nick!) believes my hesitation issues are caused by the bad oil temp sending unit which allowed oil to flow through the intake system driving temps up at the exhaust and eventually clogging the catalytic. Hopefully with these last few fixes I'll have a smooth-running GTX like old times!

Stay tuned.

Dragan.

[Daniel Roy]

I don't know what you think is an oil temp sending unit as there is no such thing on the car. There is no way any of the engine's sensor can get oil to go to the intake. Oil in the intake comes from the breather that goes from the valve cover to the black intake elbow. A little is normal, more means that the engine builds pressure in the crankcase pointing to worn piston rings. Oil can also come from the turbo if the shaft seals are worn.

Have you checked that the TPS (throttle sensor) has no dead spots in the operating range? Simple to check with a multimeter, resistance has to change smoothly, if you have any sport where you have no continuity this will cause an hesitation.

A leaky bypass valve (blow off valve) can also make the engine act weird.

Dan

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/e099705a-9dd7-4c0c-8fc5-7316c63fb03en%40googlegroups.com.

[Joel Sass]

For stuttering on my car, I've had a bad TPS give me these symptoms, for sure. I've also had a spark plug wire arc due to tiny cracks in the insulation, which was causing a sluggish issue. I've also had a drop in voltage due to poor grounding, which I fixed with multiple extraneous ground wires attached to everything along with the normal ones attached to the body. The worst of my sluggish conditions was definitely the throttle position sensor. There was a dead spot under partial throttle which caused the engine to receive poor fuel under partial throttle conditions.

Do you have a boost guage on the vehicle? I'm wondering what you're pulling at idle and peak.

Thanks!

-- Joel

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/CAPT1ejkUHesB0%3DfVYGKa6GR3F54vvjwHOopZd5xMqi2n3do3mQ%40mail.gmail.com.

[Dragan C]

Great observations: this group packs so much knowledge! Yes, I did replace the TPS - forgot to mention that in the shopping list of stuff I've done to it now.

Dragan.

[Daniel Roy]

Yes the spark plug wires do that too, I didn't think of it. Of course grounds, especially the 2 small ECU grounds that Mazda engineers thought would be a good idea to put next to the thermostat flange.

The replacement TPS, was it new or used? If used, have you checked it to be sure it doesn't have any dead spots?.

Dan

[michael reichert]

I second Dan's suggestion.

I had a problem where if the car was warmed up and thus going into closed loop mode, the engine would gradually cut out when cruising on the freeway. It could also be made to have problems if I was cruising in a lower gear on the street so that rpm was greater than 3000 rpm. Flooring the throttle  to put it back into open loop mode would cause the engine to get back to work.

I assumed TPS, MAF and distributor also. The clue to the actual problem was when I hooked a volt meter between the o2 sensor and the ECU ground wire. As the revs increased the average voltage on the o2 sensor dropped.  To the ecu this looks like the engine is running rich, so in closed loop mode it pulls fuel until the engine stalls.  Verified it was an ecu ground problem by putting the voltmeter between the ecu ground wire and the chassis ground. Which showed the same kind of problem, that the ecu ground voltage increased as the rpms increased.

Mike

[Joel Sass]

Hi Nowicksl!

In order to start a new topic, you can just send an email to 323...@googlegroups.com from your yahoo account.

On Fri, Aug 6, 2021 at 12:48 PM <nowi...@yahoo.com> wrote:

Joel, I sent two replies that are not on the board.  I do believe Dragan received them though, through the email system only.

 

Also, note that this conversation shows up in a new topic?

 

Dragan, or Joel, how do you start a NEW TOPIC?   I see no opportunity to do so.

 

Thanks.

 

From: 323...@googlegroups.com <323...@googlegroups.com> On Behalf Of Dragan C
Sent: Friday, August 6, 2021 11:56 AM
To: 323gtx <323...@googlegroups.com>
Subject: Re: 323GTX Group hesitation - fuel starvation??

 

Thanks for the feedback, gents. I should have mentioned I've already put on new cap, rotor, wires, plugs, and coil. No CEL. I'll try fuel filter next and then the pump; expect an update soon.

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/84a0c8fb-33fb-40c4-9536-a0bdc8eef70cn%40googlegroups.com.

[s n]

In response to Michael Reichert, I just solved a similar issue when warm and warm ONLY.   I went on a wild goose chase including checking all of what you suggested.  I have a second car that runs great, and I ended swapping a lot of parts that did NOT fix my problem...

With that said, my issue was a very light no load tip in throttle issue, with what seemed like one plug not firing - basically a 3 cyl car, however more full throttle would get out of the problem as well as idle was not a problem.  When cold this car ran fantastic.  That is what led me on first an electronic chase, then sensor chase, fuel line/filter chase, vacuum line chase, voltages chase, etc etc.  After a few days, I popped the rear seat and pulled the fuel pump (never been removed before), cleaned the screen, blew back and forth the lines and filter, and looked inside the tank.  Gas didn't smell bad, was no water, and the inside of the tank looked brand new (excited there!).  But the fuel looked like piss after a lot of asparagus and heavy beer consumption, really yellow.  I drained that and refilled with fresh fuel and headed to put 93 in on the test drive.  That fixed the issue.  I was really surprised the fuel was the issue for just light load driving.  Just thought I would post this for those of you with drivability issues.

Both cars running awesome!

[s n]

Well, I got ahead of myself.  The miss is back under light load, and on longer trips, say half hour or more, it gets worse with the time travelled.  Will have to look at the other solutions stated in this thread (ISC, injectors themselves, whatever), and see what I can come up with.  Will keep everyone updated as things get worked out. However I will be delayed a bit as my clutch foot decided to break a bone, and may  be a while....

[Scott Forrest]

Did you visually inspect the spark plugs for uniformity?  Mine were telling on my injectors.

Swapping my plugs between other cylinders kept indicating which injectors were likely culprits.  The inj. cleaner business confirmed which inj. were short on fuel qty and quality of spray pattern.

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/dbab78ac-6c57-4831-b2b0-295bcb55f815n%40googlegroups.com.

[Fantastic Yahoo]

Scott. Yes that was the first thing that I ever did and all appear uniform. I was disappointed they were because that didn’t provide a clue.  Changed plugs as well…..

Thank you, Steve.

via device - excuse errors. 

On Sep 21, 2022, at 11:24 PM, Scott Forrest <sctf...@gmail.com> wrote:



[Jason Culligan]

Have you tried checking the distributor? I know the springs can cause issues. That’s the only contribution I have, sorry. 

Jason Culligan

560 E Parkland Ave 

Evansville, IN 47711

812-319-2840

On Sep 22, 2022, at 8:24 AM, 'Fantastic Yahoo' via 323gtx <323...@googlegroups.com> wrote:

Scott. Yes that was the first thing that I ever did and all appear uniform. I was disappointed they were because that didn’t provide a clue.  Changed plugs as well…..

To view this discussion on the web visit https://groups.google.com/d/msgid/323gtx/AC075D6C-C372-4F85-AD4F-B41AB78C6979%40yahoo.com.

[nowi...@yahoo.com]

Jason, thanks.  Yes I have.  I have two distributors, and have changed all components including cap, rotor, wires as well.  The distributor that was in the car,  I checked and cleaned/lubed and installed, then did the same for the one from my black car which runs great.  Surprisingly no change.

 

By the way, I have a bushing to replace on the top end of the black car distributor – it was wobbly and bushing is worn out on the inside diameter.  I will be replacing that today, just as a precaution!  Having said that I have 4 more to share, and may start a post about that should anyone need one – they are NLA from Mazda.

 

Stee

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