Bogging down on acceleration and then leveling off between shifts

[sztybel]

Good afternoon, folks,

I have been doing extensive work on my car over the past several months. Primarily the fuel system. In any case I've cleaned out the entire fuel tank, replaced the fuel pump, fuel filter, oxygen sensor, catalytic converter and spark plugs.

The car has been misbehaving when put under load. The best I can describe it is it bogs down when accelerating and then levels off. With each subsequent shift it bogs down and then levels off again.

I haven't found too many threads about this particular problem. The one that did describe a problem close to mine mentions the frequency valve as being a culprit. I cleaned those contacts and will be giving it a drive again tomorrow.

If anyone has additional suggestions I am all ears.

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[Bitsyncmaster]

Have you set your mixture via a dwell meter?

Have you checked the ignition timing and that you get vacuum advance?

[David T]

Do you hear the frequency valve buzz? Checking timing, vacuum AND mechanical advance is also a good idea. Vacuum leaks can also be part of the problem As bitsyncmaster says, you should get a meter on the Lambda system and see what the duty cycle is. Does it "bog down" hot or cold or always?

[sztybel]

Do you hear the frequency valve buzz? Checking timing, vacuum AND mechanical advance is also a good idea. Vacuum leaks can also be part of the problem As bitsyncmaster says, you should get a meter on the Lambda system and see what the duty cycle is. Does it "bog down" hot or cold or always?The bogging down seems to be consistent across the board whether the car is hot or cold. It will do it while revving but nowhere near as noticeable as compared to driving it.

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[David T]

If it happens hot or cold then it isn't a CPR problem but most likely a mixture problem caused by either the frequency valve not working, a vacuum leak, or a need to tweak the mixture adjustment. You need to measure the duty cycle. If you don't get it fixed, there will be the Spring Social tech session this April in Parsippany NJ hosted by the DMA. Someone could look at it there for you.

[sztybel]

The latest update is I looked at the two areas where the banjo bolts connect to the WUR. The screen was pretty gummed up and I got that cleaned out. Car is running noticeably better, but still lacking power particularly when shifting gears. Once in gear I can slowly bring the RPMS up and get decent power.

[sztybel]

I just hooked up the dwell meter and it was reading right around 20 during idle. Then it dropped to 0. This was before the car reached operating temperature.

Any ideas on what could be the issue based on this information?

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[David T]

Did you hear the frequency valve buzzing? If the reading drops to zero either a connection to the meter came loose or you lost power to the Lambda ECU.

[sztybel]

Did you hear the frequency valve buzzing? If the reading drops to zero either a connection to the meter came loose or you lost power to the Lambda ECU.

I am going to check it again tomorrow. I was so focused on the dwell dropping to zero that I neglected to check if the frequency valve was still buzzing. It's possible that it did stop buzzing though because that connection is a bit loose.

After I disconnected the dwell I took the car for a spin. Far less bogging down (I have a full tank of gas and added BG 44K Platinum to the fuel tank). I even have much more power going up hills. Not performing at 100% but far better than the pop and lurch experience from a couple weeks back.

[sztybel]

I ran the dwell meter last night. When the car first started up it was about midway on the meter and then dropped to zero within about 15 seconds. The weird part is I can still hear the frequency valve.

It drove, with hesitation, both uphill and on straightaways. I feel like I am chasing a ghost.


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[Bitsyncmaster]

I ran the dwell meter last night. When the car first started up it was about midway on the meter and then dropped to zero within about 15 seconds. The weird part is I can still hear the frequency valve.

It drove, with hesitation, both uphill and on straightaways. I feel like I am chasing a ghost.


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Are you sure the FV is buzzing when you read zero deg? The idle motor buzzes also. If the FV is still buzzing I would say your meter is not working correctly. A good test for your meter is to push the wide open throttle switch and the meter should read a steady 54 deg.

[cpistocco]

I had a similar problem...
I was getting vacuum advance when I wasn't supposed to...
Check microswitch operation and Vacuum solenoid (which is connected to the vacuum line that connects to distributor).

[sztybel]

I had a similar problem...
I was getting vacuum advance when I wasn't supposed to...
Check microswitch operation and Vacuum solenoid (which is connected to the vacuum line that connects to distributor).So was your vacuum solenoid stuck?

I have the air box off the car and the micro switch is right there. How did you know that part was no longer doing it's job?

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[cpistocco]

So was your vacuum solenoid stuck?

I have the air box off the car and the micro switch is right there. How did you know that part was no longer doing it's job?

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Pull the vacuum hose off your vacuum advance on top of distributor.
On a cold engine you should NEVER get advance.
On a warm engine, you should not get advance at idle....only upon acceleration.

[sztybel]

Pull the vacuum hose off your vacuum advance on top of distributor.
On a cold engine you should NEVER get advance.
On a warm engine, you should not get advance at idle....only upon acceleration.

Am I hooking the disconnected vacuum line to a vacuum gauge or just feeling the vacuum solenoid for actuating in the instances described??


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[cis6409]

No need for a gauge, you can feel it with your finger on the end of the hose.

[sztybel]

No need for a gauge, you can feel it with your finger on the end of the hose.

I see. Thank you for the tips!


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[Ron]

Once you confirm vacuum at the distributor, check the timing as Bitsy suggested...at Idle AND high rev.
(Sounds a lot like low timing....)

[MikeWard]

I would suggest following this guide on checking correct routing of the vac pipes (without the need to remove the manifold):
http://www.deloreaneurotec.uk/viewtopic.php?f=17&t=4619&p=61868

Following by verifying the ignition timing is correctly set at 13 degrees btdc.

[sztybel]

Today we checked the vacuum and timing. All was good there.

However when we started checking the fuel injectors we noticed a bad spray pattern on the first two we pulled out and checked.

Does anyone in NJ offer fuel injector cleaning? I'd be cleaning all 6 of course.

[sztybel]

Update on the bogging down issue: It is gone. I ended up replacing the injectors after we discovered they were so gunned up with crap that the fuel wasn’t getting through them properly.

The car has never had more power in its life with me. It was definitely due for a fuel system overhaul but the fouled injectors were definitely the biggest difference in performance.


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[DMC-Ron]

Update on the bogging down issue: It is gone. I ended up replacing the injectors after we discovered they were so gunned up with crap that the fuel wasn’t getting through them properly.

The car has never had more power in its life with me. It was definitely due for a fuel system overhaul but the fouled injectors were definitely the biggest difference in performance.


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I'm wondering what product you chose to go with for the new injectors?
Ron

[sztybel]

I'm wondering what product you chose to go with for the new injectors?
RonI went with the Volvo 760 (022) injectors.

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