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Hesitation diagnosis help.

A friend of mine just recently fixed his 1990 245 with that same kind of issue. It was a bad fuel ecu in his case. I'd also check the fuel filter isn't clogged. Fuel pressure regulator, would also be a good thing to check fuel pressure.

Good luck with it Colin.
 
With a carburetor, those symptoms would say bad accelerator pump.
With injection, similar results with a bad throttle position switch.
Does it click just off idle to tell the ECU "more fuel please"?
Does it show proper continuity at its 3 terminals?
Did the mice nibble any wires in their temporary winter shelter?
 
MasterBlaster said:
With a carburetor, those symptoms would say bad accelerator pump.
With injection, similar results with a bad throttle position switch.
Does it click just off idle to tell the ECU "more fuel please"?
Does it show proper continuity at its 3 terminals?
Did the mice nibble any wires in their temporary winter shelter?
Click to expand...
I like what you are saying. I unplugged thr throttle position connector along with the MAF and it didn't seem to change anything with the drive ability. I need a nice diagram of the circuits and if possible start checking the continuity of every wire.
 
Here's the basic operational diagram of the TPS.
There's some disagreement over wire colors from different sources, but either way, the
center terminal should have continuity with one of the outer terminals at idle (throttle closed),
and with the other at full throttle (WOT). During normal part-throttle cruising, there should
be no connection to either of them.


240tps.jpg
 
I'd guess fuel starvation. If you're very careful and have 2 fire extinguishers ready, you can pull the fuel rail with injectors still attached and put the injectors in small jars or ziplok baggies. Disconnect and tape-off the "-" wire on the coil to prevent spark, then crank it over for a bit to see if all injectors are somewhat working and are flowing about the same. Or you can connect in a fuel pressure gauge if you have a later-model fuel rail with a schraeder valve and jumper the pumps.

How old is the gas in the tank?
 
Hello. This is an update video.

Basically the tps tested good.
I made a fuel pressure tester baser on volvoforum.uk and it was wrong spec.

Anyone know what the threads are on my fuel rail so I can test the fuel pressure?

Also why does my fuel pump work with both fuses pulled?

Either way. I'm getting closer to test more parts.
 

240 - LH2.0/2.2 help

Footnote - When a vacuum booster fails, additional air is added, which is not seen via AMM metered air...so, if brake booster's vacuum like is plugged at intake, this rules out another issue. After engine is shut off, brake pedal should still be easy to push for awhile...if hard...Bingo...
turbobricks.com turbobricks.com

This sounds exactly like my problem where do I get a known good air mass meter?
 
In your video I see a lot of smoke but I cannot understand if is due to rich fuel or oil burning.
In the latter case I think you shuld already know it's a mechanical issue while in the former, in my experience, a bad O2 sensor and/or a bad fuel pressure regulator could be the cause for rich mixture and smoke at the exhaust (especially at cold engine) but I ear also that the engine doesn't sound very well and I cannot image the cause (may be you have some duct broken or obstructed?)
I cannot say why fuel pump still run also without fuses, may be you wirings had been messed up?
To test pressure on the rail I have on my car a schrader valve, if you don't have it you must insert temporarily into the hose a T junction.
Right also the question of @bobxyz, how old it is the fuel into the tank?

You say that disconnecting the MAF the car still run in the same way but this is anomalous since without MAF the engine can run fine only at idle and with very light load on the gas pedal.
If you want to check if your MAF is working you must backprobing the connector and check the voltage between pins 3 (signal) and 2 (signal ground), you should read at idle approx 2.1/2.2 Volts but I must advice you that measuring the voltage is not a good indicator to say if MAF is working correctly or not since just a minor change of 0.1V can make the difference between a good and a bad MAF.

If you want to try a new MAF and you don't want to try the lottery of used ones I can suggest this cheap one from aliexpress marked Trofom: https://it.aliexpress.com/item/32688077154.html

I suggest this one because I had bought it last summer for my project of MAF test and recalibration and compared to an original Bosch it copies very well the signal. Furthermore I know at least 3 people that bought it too and all 3 are currently using it on their cars. The only unknown is how it will last and if it needs or not a periodic cleaning since it is not self cleaning like the original hot wire Bosch.

I share the video of the project I'm talking about since I think to had made something of pretty original and it could be of interest also to other to better understand what's behind this particular sensor:


NOTE: I't spoken in italian but I made also english subtitles

P.S. LH2.4, correct?
 
Hello

Update is the AMM pin 2 to 3 is 0.00 volts.

And o2 sensor is 0.351 volts.

So I'm going to look for a AMM before I do anything else.
 
CoconutColin said:
Update is the AMM pin 2 to 3 is 0.00 volts.
Click to expand...

This can explain why disconnecting the MAF the engine ran in the same way.
As a last check I suggest you to verify that the MAF is not working because it is broken and not because it is missing the power supply: between pins 1 and 5 you must measure 12V with ignition key ON.


P.S. to take measure you had not disconnected the connector, right? I believe that you had rolled back the sealing rubber of the connector and made back probing
 
apollokid said:
This can explain why disconnecting the MAF the engine ran in the same way.
As a last check I suggest you to verify that the MAF is not working because it is broken and not because it is missing the power supply: between pins 1 and 5 you must measure 12V with ignition key ON.


P.S. to take measure you had not disconnected the connector, right? I believe that you had rolled back the sealing rubber of the connector and made back probing
Click to expand...
I did that and got 13.4 volts. Because I did it while it was running I checked the voltage of every pin because I was looking for the hot full voltage.

I want to find a known good original amm
 
apollokid said:
This can explain why disconnecting the MAF the engine ran in the same way.
As a last check I suggest you to verify that the MAF is not working because it is broken and not because it is missing the power supply: between pins 1 and 5 you must measure 12V with ignition key ON.


P.S. to take measure you had not disconnected the connector, right? I believe that you had rolled back the sealing rubber of the connector and made back probing
Click to expand...
And yes. I back probed it connected to the amm with the rubber peeled back
 
I think on a '86, that fuse 6 is unused and fuse 4 is for the tank pump only. The main pump is un-fused off the fuel relay.

With key off and the MAF unplugged, can you measure the resistance of pin 2 in the harness to ground? Pin 2 is sensor ground and It should connect to chassis ground through the ECU. Alternately, at idle with the MAF plugged in, can you measure Pin 3 (MAF sensor voltage) to ground? It should be around 2volts at idle.
 
bobxyz said:
I think on a '86, that fuse 6 is unused and fuse 4 is for the tank pump only. The main pump is un-fused off the fuel relay.

With key off and the MAF unplugged, can you measure the resistance of pin 2 in the harness to ground? Pin 2 is sensor ground and It should connect to chassis ground through the ECU. Alternately, at idle with the MAF plugged in, can you measure Pin 3 (MAF sensor voltage) to ground? It should be around 2volts at idle.
Click to expand...
.

Update

Pin 2 resistance to ground is 0.08 ohm

Pin 3 to ground is 2.6 ohm.

Pin 3 to ground voltage key on is 0.00
 
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