Hey guys! So I have something thats leaving me scratching my head.

I have a 92 Volvo 240 (B230F, AW70) That has a weird Bog/Hesitation on hard acceleration from idle.

All sensors and ignition components have been replaced with iPD parts. Along with a new fuel tank, Lines, Pumps, Etc.

Nothing has changed the bog, It idles great and I get decent MPG (21-23mpg), But that Bog makes it a pain at stop lights in downtown. I checked the ignition timing and found that you cant change it with the distributor (ICM moved it around too hold it at the first timing mark), So it can't be that. What else can I look at? It does it both in gear and in park/neutral. Even if im already rolling it will bog.

My precious Brick in question

 

Any codes stored in your OBD1 system? (could be an air leak or air mass meter problem) Try driving with the O2 sensor disconnected and see if it still does it. - However the o2 sensor does not have any effect on the mixture during the first minute or so of operation - so if it still does it then it's not o2 related. - And you should try erasing any memory in the ECU by disconnecting one battery terminal and holding them (the two terminals) together for a minute. o2 sensors for your year are easily tested with a $10 voltmeter if you have one.

https://www.volvoclub.org.uk/faq/EngineOBDCodes.html

 

Well see I *Tried* Reading the Codes but all the OBDI system does is illuminate the LED super dim after holding the button. No matter where I insert the pin or how much I clean the contacts, If I press the button with the pin inserted in any hole the led lights up bright, But in Pin 1 or Pin 6 it just dimly glows.

I have a decent multimeter, I did replace the o2 sensor already but I guess its possible it failed, I do have a CEL on the dash now.

I will say that upon startup, When cold, It does respond to throttle perfectly but after about a minute it starts having the bog issue. That might be a clue.

Edited for Clarity

 

The ecm does not accept the signal from the O2 sensor for the first minute or so of operation. (until it thinks the Cat has heated up enough to do it's convertor thing).

Try driving the car with the o2 disconnected.

Measure the voltage from the O2 sensor. (running, warmed up, idling, plugged in, green wire is positive, body ground is the negative) If measured using an oscilloscope you will get a sine wave. From ~.2 to ~.8 volts. Your Voltmeter will flash those low numbers. Max you will see is ~1.2 volts. Min is 0. If you get a steady high reading reading - the mixture is way too rich. If your reading is 0 - it's way too lean.

You need to get your odb box to work -------------------

 

After just living with the issue, it began too get worse, It began too stall completely under any throttle and backfire repeatedly through the intake. When it does run, the idle is very very high. if its already running and driving above 2k rpm, its sings like a dream.

I DID get the OBDI reader too work, and got the following codes: 322, 121, 133 from Pin 2 and a code 111 on pin 6. I know that code 111 means no codes, But the other 3 seems too point towards the MAF. The car WOULD get an OCCASIONAL CEL randomly but it would go away after a day. I also found that the intake flapper thingy was stuck closed and had been for some time (The flap had somehow welded itself too the cold side inlet) so I wouldn't be surprised if the brand new MAF Failed. What's your say?

 

Back fire from the intake is usually caused by a lean mixture. - and will also blow aux air hoses off (there's no clamp on them on the manifold), making the mixture even more lean! Back fire from the exhaust is caused by a rich mixture -

And Yes, my shops probably replaced hundreds of air box thermostats. (on 240s) It was an item we would check at the 30k interval services. When they go bad the cold/hot air flap gets stuck in the hot air mode - and possibly helps to fry the AMM. (in warmer climates)

 

That's what's confusing me the most, even when fully warmed up and at any throttle it smells like a carbureted car, lots of unburnt fuel, which also could be the lack of a cat, (I found a lot of dust in the resonator, I had too replace it, when I looked into the cat it was empty).
I was concerned it was a valve timing issue but the belt appears new and is on time.
I also tried using carb cleaner and spraying any gaskets I could see while the car was warm too check for vacuum leaks and saw no idle change.

I'm going too replace both the 02 sensor and MAF again, they're both only 2 months old but iPD gave me a warranty. We will see what happens unless you have any other suggestions.

 

I'm also concerned about a "Pink Label Bosch Box" causing issues. Would a 1992 have a faulty injection computer?

 

1. Nope, lack of cat is not creating the unburnt gas smell. Incorrect mixture/not firing correctly is.
2. I would not expect either of those (new) parts to be bad. What brand of air mass meter? (yes you do have 2 AMM codes, so maybe- )
3. Pink label control unit - what goes wrong with those is they stop turning the fuel pump relay on. So if the fuel pumps are working - you have a good pink box.

What's the voltage coming out of the o2 sensor (disconnected) when running and warmed up? (from earlier ~.2-.8, fluctuating between)
What's the fuel pressure?
What's the condition of and resistance of the speed sensor?
Air intake hose is intact/no leaks from air mass to throttle housing?
What's the compression?
Condition of the rest of the HT ignition? (plugs,wires,cap)
Are you sure the intake manifold gasket is not split near cylinder 1?
Does the car have the correct rotor button? (Below is the wrong one - correct one has a larger contact on the tip, and I trust you did not twist the distributor and the cambelt is in the correct position on the jackshaft pully)

 

Forgive my seeming inability too figure out this forum's Quoting system.

I haven't checked it yet, its a month old, I will as soon as weather permits

Unsure as well, the original owner replaced the entire fuel system, from tank too lines too injectors too rails etc etc etc. The external pump is very noisy, but both the Volvo branded and Bosch branded pump I bought make the same racket. appears too be OK. I have no way too test it at this time. (Shoe String budget, Moving in 2 weeks)
What Speed Sensor are you referring too? Do you mean the sender on the transmission? I know that the ABS system is 100% as well as the speedo being spot on with speed (Except for an occasional flutter when driving below 20mph, rarely happens though)

All brand new. I must also once again mention I sprayed carb cleaner in every nook and cranny and listened for a change in idle and it did not occur.

129psi. 131 psi, 132 psi, 130psi (Dry Test, figured with numbers that good I didn't need a wet test)

All Brand new, I must mention all of the parts are either Bosch branded or Volvo branded. I ordered them from the Dealership when I got the car before I found out about iPD. The only original thing is the distributor itself, but it has no sensors or wires.

\
I bought a new gasket just in case. However again I didn't find any leaks upon visual and flammable aerosol inspection.

Yes, it's blue and has a wide "finger", much wider than what is shown in that picture.

I checked timing on the distributor, 10Deg BTDC, However adjusting the distributor made no change (Ignition module, I'm not use to all of this technology!) So I set it back too its stock position.

Now that is one thing I should check, I know the belt itself is in good shape, although I'm not sure about anything else.

Sorry for some of the wordy responses, I'm trying too keep "link rot" from occurring, I have a video of the issue as well and will post that ASAP.

And Sorry for the delay! We are having some unforeseen weather in SC, (the car is also running NOTICEABLY worse in this cold, sometime not responding too throttle at ALL)

 

The following is the aforementioned video, On todays test drive it actually stalled under normal driving (not during accel/decel) for seemingly no reason then came back too life after a few seconds, at which point the stalling issue went away for about 5 minutes then came back.
This is me apply quick blips of throttle up too 75% (Any higher and it will backfire and stall out completely)
Video of Angry Brick

EDIT: Also note the buzz of the fuel pump in the background, unplugging the in-tank pump does make it run worse as-well. The exhaust also now "crackle-pops" from excess fuel.

 

1. Usually an indicator of fuel pump or pressure problems
2. Engine speed/position - on the flywheel. The insulation/shielding on the wiring comes apart
3/4. If the jackshaft is off a tooth or two (or someone took out the block and twisted the distributor) - the rotor button will not line up with the pole in the distributor - and the spark will have jump further in the cap to get to where it should be going. And yes the distributor simply distributes the spark - what triggers the coil is the engine speed sensor (and the control unit) Simply make sure the rotor button is lined up with the mark (notch visible with cap off) on the top of the distributor when at TDC

 

I'm leaning towards a bad MAF and fuel issues, Although the entire fuel system is new, Even the lines and Tank. Unplugging the intank pump makes the external pump louder. Maybe its that pump?

Oh! you mean the Crankshaft Position Sensor? I had to replace it. It did exactly what you said. Except when it died the car wouldn't start.

As for the distributor. It's only ever been moved by myself. It was corroded into the block, aswell as the little plastic buffer too keep tampering from occuring had rotted. It is set properly.

Is there an under hood access port too the fuel rail too check pressure? What should the pressure be?

 

After Performing Testing of the o2 sensor, I got readings between .30-.89v, sweeping back and forth, cycling every 3 seconds. So I assume that the 02 sensor is OKAY.

After letting it warm up, it got even worse, it is now hunting for an idle after warming up, The codes remain the same however, before when I had these issues it ran like a dream at idle, Its a slight hunt, more as if it's bogging itself every 3-5 seconds.

The Intake boot-hose-accordion thingy is apparently actually OEM and original, (Guess the seller wasn't so straight forward) However when I pulled it off and inspected it it was really clean but there was some kind of clear yellow silicone blocking 2 cracks. i sealed off the ends and blew into it and other than expanding it held pressure and had no oil residue.

After testing fuel pressure with a little Schrader valve on the fuel rail, I got 36-39psi at idle, and 40psi steady on accel, even during bog.

I'm seriously at a loss for words with this machine. It ran so well a month ago, I'm ordering a MAF sensor tonight so we will see how that goes I guess.

 

While I wait for the AMF(MAF) sensor too arrive, I decided too clean the one I have and change the sparkplugs...

While the Sensor cleaning made no difference, I found that the AC/Delco plugs that where installed where wrong. When I tested the compression I did notice they where loose but having never worked on one of these motors I assumed they where just old, NOPE, The NGK R plugs I replaced them for where much larger and had a far smaller gap. After replacing them, it almost took away the bog! Not completely however. It is FAR more likely for it too back fire through the intake when pressing the gas. Not sure why, But when the new MAF comes in tomorrow night HOPEFULLY that will be the end too this saga.

Old 5.3L Chevy plug vs New B230F Plug

 

I trust the plug on the left was not installed in your Volvo. (there's no gasket, just a chamfer style seat!) For back firing - that is either too lean/engine overheating/cam timing wrong.
Question - "Condition of the rest of the HT ignition? (plugs,wires,cap)" from earlier in the thread. Start with the basics before replacing expensive parts.

With correct plugs/ignition parts/no air leaks/etc - before installing a new AMM - hold the battery terminals together for 15 seconds (some say longer!) to drain any possible memory from the control units. Then see how the engine runs.

For a parts supplier - eeuroparts or fc euro are good choices price wise. If you want dealer only parts - voluparts.com sells dealer parts at least 10% off list.

- you can artificially make the engine rich or lean, (to test the systems are working) by controlling what the O2 sensor is telling the control unit. (your .3-.8 sounds normal)
with the O2 unplugged - ground the green wire (going to the control unit) - that will tell control it's lean (0 volts) and will richen the mixture. To make the mixture rich - hold the green wire in one hand and touch the positive terminal with the other hand (finger). This will supply a small voltage to control telling that it's rich (high voltage) and lean the mixture out. (as much as the O2 voltages can) This can make sure the AMM is sending a close to good enough signal of volume/temp/mass.

 

I know! I have no earthly idea why I never investigated how "loose" they where, Nor how they even stayed put!

I tried that o2 Sensor trick (Shorting the green wire too the chassis) and IMMEDIATELY noticed a HUGE difference. The unburnt fuel smell worsened slightly, Until I revved it. INSTANT acceleration, no bog! When I did the through-the-body-positive trick, It IMMEDIATELY stalled out.
After plugging it back in, it went right back too the same old "Bog/stall when touching pedal."

After doing that master reset, I'm even closer! Now if its at idle with no load, throttle response is instant, However in gear it will still try too stall out if I hit max throttle from a dead stop. HOWEVER, I no longer have any backfiring through the intake and the unburnt fuel smell is gone! I'm really hoping this new MAF fixes my last issue.

I also need too look into how too clean/replace whatever a "flame trap" is.

 

Mini Note:
​​​​​​It just backfire through the intake on decel so hard it detonated the entire intake system. Airbox, filter, Intake hose, Maf, and took a radiator line with it. All of that just turned too plastic shrapnel. Including a million tiny dents under the hood. Valve timing is still correct however. It also started stalling again (It kept running! Like sh*t, but running! No misfires either!)

I'm loosing my mind with this d*mn car!

 

I managed too limp the car home, meanwhile the entire car wreaks of fuel now, which seems too be coming from the now exposed, unfiltered intake.

 

ANOTHER UPDATE: I rechecked the timing belt and the timing is still properly set (and no sheared pins or bad cogs/gears). It is back too running with no hesitation, but now it hunts for a idle. However there are no codes. I checked ignition timing again and found that it was still holding about 10-15Deg BDTC at idle, ramping up towards 0Deg upon accel. Is that proper ignition timing?

I also took this time too test for vacuum leaks by palming the now open intake tube. it immediately responds too being covered, and just being covered halfway immediately stalls out the motor. So atleast I know there are no vacuum leaks present.